Need Help! Bigger Tires?
 

If anyone is following my other thread they may have seen that my tire and rim got messed up by a large chunk of concrete in LA yesterday.

I need a new wheel and since I was already thinking about putting larger wheels on, now would be a perfect time. If i do it I'm only going to go from R13s to R14s. This would be a 7% decrease in rpms. I'm going to only put the biggers ones on the front so i halve any weight increases and spinup losses. I have no rpm gauge, but it feels like the car is geared too high on the highway.

My car has plenty of power going uphill and I'm going to take out at least 25 pounds of weight if i do this.

I am worried about messing up the torque.

Do people agree that this mod makes sense to do?

Thanks for the help.

A 7% increase should be fine.
You will even find that you have more tire selection with 14 inch wheels.

What is your lug pattern and stock tire size?

Mazda Miata and MX3 stock wheels can be found for cheap and are decently light. My MX3's are ~12.5 pounds a piece. They are 14x5.5".

If you want the best mpg tire... Bridgestone Potenza RE92 165/65R14 @ 50-55 psi :thumbup:

I'm running a cheap Chinese tire that is 1" bigger than stock, 24.3" vs. 23.4" I have done very well with them, even with the tires being non-LRR and bigger than stock.

Here's a pic of the tire
 

TY for the help

4 lugs

I'm thinking i might look around a junk yard. What else might work for my axle?

It looks like 4x100, though it could be 4x108. A quick Google search would tell you exactly.

You'll be lucky to find any lighter weight alloy wheels in the JY. Most of what I see are steelies that weigh 20-25 pounds/piece.

Craigslist has been my best buddy when it comes to finding wheels. And Car-Part.com--Used Auto Parts Market

A 1988 Corolla has a 4 x 100mm bolt pattern.

Thanks Gasoline Fumes :thumbup:

There's a few options on LA's CL. Some light HX wheels and steelies.

https://losangeles.craigslist.org/se...l&query=14x5.5

I see mention of one spec, but there are three you need to consider/match

Bolt pattern you know about, the 4x100mm, and that's foolproof.

Center bore, the center hole in the wheel must match the hub or you can't balance it. Spacers get lost. Get this right.

Offset, be sure to get FWD wheels, high positive offset, if you like your drivetrain to work.

HAve fun,
Frank

Another concern is the lug nuts when using different wheels. Honda and VW use a ball seat and Toyota uses a tapered seat. Honda lug nuts will fit Toyota studs.
http://ecomodder.com/forum/attachmen...1&d=1449817855

Is the center bore really an issue? I just put Subaru wheels with larger center bores on my mother's Prius for the Winter. Seems fine so far with the lug nuts centering the wheels. And I look forward to the wheels not getting stuck to the hubs over the Winter!

Ok, I think there is some confusion as to the effects of different wheels/rims. Changing the RIM size does not change the RPMs at all, it is changing the TIRE size that affects the RPM, specifically the overall circumference of the tire. Now a different rim size may allow you to choose a different tire size to change the RPMs, but if you switch from 13” to 14” wheels but put the same size (diameter) tire on them, your RPMs won’t change at all.

Tires
 

Yes aardvarcus. That is correct. I was originally thinking r13 meant an outside d of 26 but no.

The tires I'm replacing on the front drive train are 175/70r13 meaning fresh tires have an od of 22.5" if the math is 13+2×3.23×12×.60×175/1000
The tires are currently about 21.35 inches with load on them.

Does this mean mile odometer is counting miles short? Does the odometer compensate for changing tire sizes?

Also the current tread style seems pretty good (see pic) but the tires are only rated for 44 psi max. I'd have to get a similar tread and width to not negatively effect my mpg but if i get something with a higher psi rating and go a little bigger i should improve mpg a noticeable amount I'm thinking.

@fbov - so all the weight from the car gets transfer to the rims where the center bore contacts the axle? The lug bolts don't take the force?

Also there is the possibility of just using the dinged rim and getting new tires (it's not too bad, but I think it is probably permanently off balanced and may leak air) What do you think? The tread is so worn down that I'm losing almost an 1 & 1/4 from the new size (does that sound right?)

I think the max outside tire diameter I want to go with is 23" (compared to current 21 3/8")

I have 14" stock wheels and just bought a set of 15" wheels. Both are wrapped with 195/60 tires for a 1" diameter increase which equates to a 4.1% decrease in RPMs. I get lug bolts Monday so I'm hoping that the larger size will give me a slight increase in fuel economy.

If you drive in your torque band then the size increase shouldn't cause any consequences except less fuel being used. Any larger of a tire and it will probably have a negative impact especially when outside the torque band. A narrower tire will give less resistance and a little better fuel efficiency which might come in handy with the larger wheel and tire size.

Doing the Math
 

Toyota 4A-F and 7A-FE engines

According to this chart, my engines torque output is pretty much flat after 2500 rpms.

Since I don't travel really less than 60 on the highway I'm guessing this means that I should aim for a tire size that gives me 2500 rpms at 60 mph? And then any speed beyond that is good as far as torque is concerned.

The one issue I have is that the torque output is at full load... We're hardly ever driving there. However, I guess this makes sure that all the parts can handle the increased torque load from bigger tires.

Anyways my car has no tachometer on it, so I looked up my gear ratio for the three gear A131 Auto Tranny to deduce my rpms.

1993-1997 Toyota Corolla transmissions and axles

Right now I'm going 3330 RPMS at 60 mph with my worn tires at 21 3/8 OD and with new tires at 22.5" OD that are the same it would be 3180 RPMS. Still high.

So if I were going to go 2500 rpms at 60 mph, that would be a 28.22 OD on the tire.

I think I'll go for 2800 rpms just to be on the safe side, so that yields a 25" OD.

That doesn't sound too drastic. A 10% change from stock conditions, 15% change from my current worn tire conditions.

Darn, that is quite high. In my Golf MK3 with stock 195/60/14's I am at 3000 at 75 and about 2400 at 55 with it increasing 200 RPM per 5 MPH higher.

I'm looking forward to my 195/60/15's to lower that.

I think you will quickly see problems with a four inch larger tire. When turning the tire will more than likely rub the wells. I put 33 inch tires on my car that had 28 inch tires stock and it rubbed bad! Looked cool though! LOL

I am going up one inch in diameter with my swap and might even push it another half inch or so larger when I get new tires. That is about as large as I could go without narrower tires since it will start to rub when turning if any larger.

I've spent the whole day learning about rims and tires.
I'm realizing there are a lot of variables.
I found a good website to buy tires. You can basically get exactly what you want for a good deal plus it's easy to see if a particular tire size exists.

Cheap Tires Online | Find the Best Deals on Tires | SimpleTire.com

I think overall the best and most cost effective thing to do for a non-hardcore ecomodder* is to up the diameter on the drivetrain wheels*, keep the non-drivetrain wheels the same (or even go smaller D to help reduce weight and radial inertia) and reduce the width on all tires to the smallest size your existing rim can take (which will probably only be a cm or two so your grip will be hardly effected much but the weight and drag will be lightly effected for the good).

If you are hardcore I would reduce the tire width by an appreciable amount which basically means getting new rims.

You can become hardcore by turning your engine off while on nice coasters and then using your e-brake to slow down so you don't lose break boost. And this should help to wear your tires more evenly if you have a FW.

You can then put the tires on yourself and then get someone with a Cosco card to balance them for like $3 a tire.

Plus you have to be careful that things don't rub - very bad things can happen!! 7% sounds like a potential problem.

So many good points in this thread. Good conversation!

The key thing to remember in all of this is balance. There are good and bad effects of making changes. For instance, most cars are under-geared (IMHO) so that they "feel" peppy. Going to a larger tire diameter helps that, but only moderately.

Also, as mentioned by aardvarcus, it's the total rolling size, not wheel or tire. I just changed out 18" rims with 40's (summer sport tires) for 16" rims with narrower 70's for winter. Overall diameter is virtually the same, snow traction is immensely better.

Yes, narrower tires are better (usually) for rolling resistance and aerodynamics, but worse for traction (except in snow) and usually worse for ride and much more susceptible to damage in a big pot hole. Also will decrease braking capability.

The down-sides to larger diameter tires: 1) it lifts the car causing a increase in Cd, more drag, (all else held constant). Greater ground clearance may help with parking lots, but not with aerodynamics. 2) can interfere with internal clearances (just make sure they don't rub anywhere). 3) will change some of the vehicle dynamics (like turning capability) if you're into pushing the limits ....

Changes in wheel size is not compensated by the speedo or the odo. Most cars indicate higher than you are actually going, so check that with a stop watch and mile markers on the highway. Exactly 60 mph will take 60 seconds. (Most cars read 2-5 mph more than your actual speed.) Odo's, on the other hand, are pretty close to exact with the stock spec tires. Increasing size will show slightly fewer miles, but that's not worth the hassle unless you are really crazy about exactness -- in which case you should use a GPS to measure miles instead of the odo. (As a side note, your fuel econ measurements will be difficult to compare if you're using the odo because of the error you'll introduce with the change.)

Finally, I strongly suggest you don't mix and match sizes. Unless the car was made specifically for it, or you specifically want some other effect of size (think 60's muscle cars and dragsters) I'd keep them the same. Makes lots of things less complicated like rotating tires for best life and uniform wear, flat changes, spare tires, etc.. Increasing tire size will change the vehicle dynamics anyway, but making them different sizes may change more than you want.

Great discussion by everyone. Thanks!

Good Points
 

Good Points Design

In my case I'm in the process of doing re-doing the front air-dam because a huge rock went through it, so I'll be able to compensate for lifting the car 1.5".

I think there are definitely some benefits to be had for people more than just your casual ecomodder that can be achieved as easily as just buying new tires that are different on the front and back. The big thing being you don't want big tires on your non-drive train wheels because they are more weight and have way more radial inertia.

In terms of wear, I plan on using the e-brake handle more often to wear the tires a bit more evenly.

I'm glad you bring up the point of getting a flat. I think if you put a donut with a big tire on the drivetrain you'd proably destroy the diffy after 50 miles. Might be OK for going 5 miles at 30 mph though. I think the solution here for getting back home on the freeway is to take your back tires off and put them on the front and then go with the big and small guy on the front. (And be the slowest guy on the freeway, which you're probably really good at anyways if you are a dedicated ecommodder:)

You have a point with narrowing the tires and going over potholes. But I gets a bigger OD, then the taller walls will have more shock absorption than not having taller walls (as long as it is still a passenger class tire) so that should compensate for a slightly smaller width.

I don't think non drive tire size(diameter) plays too big of a role since the engine is not required to power those wheels specifically. If you have smaller non drive tires they will wear out quicker as they are turning more per given distance with both sizes of tires being completely equal in construction and materials. It also turns the bearings for the hubs more which wears those.

If you get a half percentage point better gas mileage but have to buy wheel bearings or tires sooner than you really haven't made any headway and are actually going to lose money instead of saving.

Remember: I am not schooled for this kind of stuff so I could be completely wrong. Just my thinking on the subject...


Of course you could get the smaller tires and try it out. Although I think the savings are going to be pretty slim if any and could be inside the margin of error(wind, temperature, etc differences when testing).

A couple of thoughts:

First is that tires deflect and the revolutions per mile is NOT what one calculates using the outside (freestanding) diameter. It's about 3% lower than that. Be sure you remember that when you do your calculations.

And, Yes! your car does NOT automatically compensate for the changing tire diameter. As a general rule, the speedometer is driven off the output shaft of the transmission. So when you change tires, you need to be aware that your speedometer and odometer are in error.

Having different tires front to rear MAY cause some emergency handling issues. The problem is that you will NOT know that until you are in such a situation - and then, it is too late. Frankly, I would make a complete changeover, rather than piecemeal.

Well i couldn't find the right rims for what i wanted so i just bought the biggest narrowest tires (p165 80 13) for the existing rims on the front. Im bummed i couldn't get bigger rims that work but i dont want to waste anymore of my time on this and i need tires. Still a 1 inch improvement though and tad narrower. I was at the junkyard today and noticed a 155 width tire on a r13x5.5 rim (165 is the lowest recommend 175 is stock). It seemed to be worn fine so I'm putting that size width on the back. I'll definitely find a good spot to do some crazy turns to make sure the back doesn't slip out or the 155s break their beads.

I got my lug bolts for the new rims today so I've also got larger tires and rims on. Aside from the faster acceleration I did notice that I am using less gas by checking the Torque app for fuel economy. This was in urban driving with less stops up to 40 mph.

Another thing to think about is deceleration cutoff.....

If you don't know what that is: Deceleration cutoff is where the car will turn off the fuel flow when the accelerator is not pressed and RPMs are above a certain number, usually about 1600, so the car just coasts in gear but uses no fuel. Not sure if your car has this feature but with larger tires the engine will be spinning less for a given speed effectively changing when you will enter deceleration cutoff which may negatively affect the MPG. I did notice that in certain circumstances where I would normally be in Decel mode I was still using fuel. Instead of having no fuel flow I would see that I was getting roughly 60 MPG while coasting meaning I would have to downshift to second which would cause the car to slow down too quickly. It was late and I may have had my foot on the pedal while coasting so it might have registered that and kept it out of decel mode so I will have to test it in the next couple days.

This is with 195/60/14 --> 195/60/15 tires and rims.


Let me know how you get on with the narrower tire. I'm thinking about heading to the junk yard to grab some narrow taller 14's for my steelies.

Got my New Tires On
 

I'm so excited I got my new tires on by myself! I can't wait to see how much better my fuel mileage is going to be.

Not only are the tires overall lighter, but they all are narrower and the drive train has a larger diameter to reduce engine RPMs.

How much does everyone think my fuel mileage will increase by?

PS. If anyone is wondering how they can put their tires on themselves and save a bunch of money, check out the videos I made.

Setting the bead with a leaf blower:
https://www.youtube.com/watch?v=lCYNkpNL2V8

Redneck style of removing a tire:
https://www.youtube.com/watch?v=lCYNkpNL2V8

Using an oven and freezer to assist with putting a tire on a rim:
https://www.youtube.com/watch?v=zMASfv2cLGk

I noticed in my own testing that I was never really utilizing fifth gear because it caused my fuel economy to go down. The only time I used fifth was following behind trucks at highway speed. So I might as well have a four speed transmission now that I have larger tires. I'm not complaining though. I am getting better gas mileage in fourth with the larger tires than in fifth with the smaller tires.

My drive shaft fell off the transmission the other night as I was leaving a rest area so I ended up staying overnight in my car, so with four hours of idling for heat and 265 miles I have used 9.5 gallons. Taking into account the .5 gallons per hour of idle, I got about 35 miles per gallon so I would have to think the extra 6 miles per gallon over EPA were in part due to the larger tires and my new driving techniques. Only 150 miles of the 265 were with the new tires.

Also, keep in mind that lower RPM's does not automatically equal higher fuel economy. Engine load has a lot to do with it:

If I am in third gear going up my hill which is pretty steep then I get about 28mpg with a very slight slow down. If I throw it into fifth then I get about 12mpg even with the lower RPM's because the engine is requiring more fuel to do the same amount. This is more so evident when you have the larger tires on when going up hills.

On long flat roads drafting is your friend, especially with the larger tires. Your car will use much less fuel to turn the extra tire size.

And to answer your question:

I am guessing you will see a 4-5% increase with the same driving.

This link says your RPM's at the tires will drop 3.3%: https://www.tacomaworld.com/tirecalc...0r13-165-80r13

@dfeldt91

That's a bummer about the drive shaft. What kind of car is it? Did it come off while turning real hard?

I do have good news. The car glides now. I don't think i even need to get the wheels balanced. I'm barely pressing on the gas on the highway and she's super smooth. I'm pretty sure I'm going to get 45 mpg tank in the near future.

The drive shaft fell off because I assumed my friend tightened the bolts since he put that side back together after swapping the clutch. He assumed we were just finger tightening them at that point and didn't bother to tell me. I pulled in to the rest area for a break and backed up then put it in gear and it just revved as if the car was in neutral. It made a clunking sound so I assumed my new lug bolts were the issue and maybe one snapped. Looked at them and they were fine then got under the car and saw six 5/8" ball bearings on the ground...oops. The clunking ended up being the last bolt that was holding it together snapping since the others had already backed themselves out. It is a 1997 VW Golf. Cheap fix though, CV shaft was $15 at the junk yard and I only had to undo the large bolt at the end where the brakes are to get it out.

If the tires feel smooth at speeds of 60 mph then I would say they are close enough to not need to be balanced. At least I wouldn't bother. I paid $65 to get mine dismounted, cleaned, remounted, sealed and balanced for three tires. My new rims and tires were on a car that rolled so there was dirt in the bead causing them to lose air. They are doing well now though!

What were you getting before the tires mpg wise??

My record was 40 mpg a few tanks ago. I've been getting 36, 38 mpg tanks with one 32 due to me running wide temporary tires.

That's good the car's fixed. It sounds like you didn't have to pull the tranny or anything.

Record
 

My record was 40 mpg a few tanks ago. I've been getting 36, 38 mpg tanks with one 32 due to me running wide temporary tires.

That's good the car's fixed. It sounds like you didn't have to pull the tranny or anything.

#$%$%^^^

OK so I"m angry. If anyone is following they could see I put my tires on myself. So somewhere in the process of me putting my tires on myself to getting rear endeded to the point where my trunk does not open right now... i'm getting worse gas mileage. 36 compared to a 41 max recent. To Be more true to reality.. I warped my rear rotors (both passenger and driver rear {I'm hoping gfront'ts aren't F'd).

Long story short what should have been a easy hpyothesis and implementation turned into odo-meter let-Down.

But the good news for anyone considering this mod is there is still hope.

My Hubs's got warped.

So I never got to see if narrower tires and larger drivetrain/ reduce RPMS reduces MPG.

I got to raise the front end up still and make sure the tires don't have a jacked up sway (as in I jacked the car p and free spun the wheel and could see a visible sway).

Both reaer ends had this, 1/8 to 1/2 lateral sway result in significant vibes at 60 yo 75 mph. And the tires were abnormally hot upon just checking.

So i'm thinking if I fix everything I should achieve record mpgs with the DragBean (especially since the new tires were Noise reducing and narrower width).

Thisis unfortunately turning into a money pit instead of a saving mond.

Maybe because the rims from the self installation bent them.

Or maybe beause I did not use a torque wrench to mount my wheels.
...
All I know is I have to fix this so I can prove that narrower tires and bigger tires to reduce drivetrain RPMS works...

I don't think the lack of using a torque wrench would have warped your rims. Not many people actually use a torque wrench to install the wheels. Most shops just throw the impact to them. I like to finish mine by hand with a socked/ratchet, then drive the car forward and backwards a bit, and then re-tighten them.

You mentioned you mounted your wheels and tires yourself, but did you have them balanced? I usually take my loose wheels and tires to a tire shop and have them mount and balance them for me. Usually they don't charge as much if you bring them in loose and if you take the old tires with you.

Don't get frustrated by the setbacks, use them as a learning experience. Ninety percent of everything I know about cars is related to a prior bad experience and my desire to get things fixed correctly. I know that is easier to say after the fact than in the moment, but we have all been there.

So I've figured out if you got a warped hub and put good rims on the warped hub, it will warp the rims.

While I was driving on a long 700 mile round trip for work I stopped at a junkyard real quick and pick two good wheels for $20. I spun the wheels on the back hub of the car I picked them from and they had no whirl or anything.

After about 50 miles of driving with the new wheels the vibrations came back.

The same thing happens if you put bad rims on a good hub.

I'm kinda assuming the brake drums are bad too.

Basically any warp is contagious.

I havn't tried rotating the wheels 1 or 2 lug nuts on their perspective hubs yet, maybe that would hopefully fix the problem, but I think I have to replace everything to realistically fix the problem. (I can probably get the brake drums turned though).

So now I'm dealing with basically two badly warped hubs in the back, 4 bent rims (including the two picked ones), one of my front tires got slashed, the lug nut on one of the front hubs gaulded and snapped off, and so now I'm going to have to replace that too.

I think the best way to deal with this is to just replace all 4 bearing, hub, and rim assemblies with picked parts and hope the picked parts are good.

The car already has almost 250K miles on it, so the other thing to do would be just to drive it until it gets really bad or the engine dies. This option is a little more dangerous because the handling is not going to be right.

Another question is, how much worse gas mileage do you get from warped hubs? I'm getting about 35 mpg right now, down from 40 with the wider tires. Hopefully it doesn't get worse. I'm pretty certain the warped hubs and tires can be blamed for this nearly 15% drop.

DragBean,

First, you need to find out who has a Hunter GSP9700 Road Force balancer - and make sure they know how to measure a bare wheel.

Second, I don't think a warped hub will CAUSE a warped wheel, but a warped hub will wear a tire irregularly - which will behave like a warped wheel.

my $0.02 FWIW: #1 tires don't get hot unless they are driven hard or for long trips at low pressures, or the vehicle is driving sideways.

#2 take off the wheels and MEASURE hub wobble on ALL the hubs. for this purpose, any measurement method will do as long as it is consistent. straight stiff sticks, last word gauges...... whatever. I can't see how all 4 can be thrashed unless you off road A LOT, or slam into curbs daily accident or not. if they all measure the same, your measurement system is garbage. 0.060" or 3mm is kinda OK for now, specifications should be about half that at the rim edge.

#3 if the hubs wobble, you either have bad bearings or warped hub. NOT TO WORRY. bad bearings you'll hear, bent hub can be shimmed temporarily for testing

which ever hub is the least wobble, mount the rims and check wobble one at a time. 3 lug nuts should be sufficient but use all 5. Torque them tight. if they are all consistent see #2 above.

Take the rim off and rotate it about 180 degrees. if the wobble got better, mark this position for later. if the wobble got worse, you have a bent rim which is very possible. measure best wobble write done that number. standard 1/2 inch Home Depot washers are either 0.060" or 0.030. stack the appropriate thickness on the hub at the point of least wobble. install and tighten down the wheel. wobble should mostly go away. If it got worse, mount washers on other side of hub studs 180 degrees from where they were.

report these findings. we'll go from there. it is a PITA, but will give usable data .

No Noticeable improvements
 

No noticeable improvements besides for one occasion when I was transporting 400 lbs in the car on the highway and I got one of the best tanks ever.
Maybe the slight lift the wheels did negated any gains the transmission might have had?