Topic has probley been discussed too many times but I never heard too much about comparing the side walls from a low profile tire to a larger profile tire.

In the next few months I'm going to purchase a new set of low priced wheels. So far if I go for the 15's I would buy a nice set of Rota's (about 12lbs) or another light weight brand. If I buy the 17's my local shop has a good deal on the CP8R (12lbs). Now I just checked Toyo's site and for the Proxes tire, both the 205/50/15 and 205/40/17 weight the same, 18.5lbs give or take.

My question is if two wheels are the same weight would the stiffer sidewall be more useful in autocross? I know there is a larger selection of tires for the 15's but seems like a better choice to go with the 17's. Also from my personal experience always felt like my car handled much quciker with 17's than 15's.

Any comments are welcome.

Thanks,
Rob

 

The thing is, with the 17's, the weight is all right at the outermost point, where you don't want it.

Tirerack did a comparison test with 15, 16, and 17 inch wheels a little while back. I think the 17's ended up being the fastest. Go read that and make your choice.

As for the rubber...definitely a better selection and prices in the 15" size.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mojo-Jojo &raquo;</TD></TR><TR><TD CLASS="quote">Tirerack did a comparison test with 15, 16, and 17 inch wheels a little while back. I think the 17's ended up being the fastest. Go read that and make your choice.
</TD></TR></TABLE>

Don't forget all the facts. Each time the wheel got bigger they put wider tires on. I believe it was 15/195 16/205 17/215. Hardly a fair comparison. Oh, and I believe it was GRM not TireRack who did the test.

 

Here's the link for the Grassroots Motorsports comparo.

http://www.grmotorsports.com/plustest.html

Rob

 

I've raced on my 17" Superleggeras, which are actually lighter with tires than my 15" 2000 Si wheels with tires... the 15s are still faster. Less inertia makes the difference.
It depends on the course... on a tight twisty course... the wider/low profile tires might help... but if its a little more open, then 15s may help. I never tried both on the same course, so for head to head comparison, I don't know. The car did feel more light-footed on 15s though.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Boilermaker1 &raquo;</TD></TR><TR><TD CLASS="quote">I've raced on my 17" Superleggeras, which are actually lighter with tires than my 15" 2000 Si wheels with tires... the 15s are still faster. Less inertia makes the difference.
It depends on the course... on a tight twisty course... the wider/low profile tires might help... but if its a little more open, then 15s may help. I never tried both on the same course, so for head to head comparison, I don't know. The car did feel more light-footed on 15s though.</TD></TR></TABLE>

Thanks for the post Boilermaker1.

I'm looking some nice wheels and think the 17's will fit my needs best. Later this season I would like to attend a local autocross and maybe a track school with the car. Since I'm not going to do more than a few track sessions I think the wheels will work.

Rob

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Geratol &raquo;</TD></TR><TR><TD CLASS="quote">

Don't forget all the facts. Each time the wheel got bigger they put wider tires on. I believe it was 15/195 16/205 17/215. Hardly a fair comparison. Oh, and I believe it was GRM not TireRack who did the test.</TD></TR></TABLE>

Oh, yeah. Good point. And it was GRM, but I think Tirerack provided the wheels and tires. I read it from a link on Tirerack way back when I was picking out my wheels.

 

I really dislike that article because everyone who reads it comes to the same conclusion that 17's are better without looking at all the details. It's great for The Tire Rack because 17' tires cost more.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Geratol &raquo;</TD></TR><TR><TD CLASS="quote">I really dislike that article because everyone who reads it comes to the same conclusion that 17's are better without looking at all the details. It's great for The Tire Rack because 17' tires cost more.</TD></TR></TABLE>

I agree that Tire Rack probley had a little "agreement" with GRM for the outcome of the test. When the drivers commented on the tires they even said that the larger wheels were noticably slower on takeoff. Especially since the 17" wheel they used were not light weight but heavier type wheels (20lbs.).

My only problem with 15's is they feel less responsive than 17's. Maybe it was my choice of tires, Kumho 712's, but they really felt almost like my stock 14" steelie tires.

Rob

Rob

 

Here's something to think about:

Some people claim that larger wheels are more "responsive" (I have never noticed), but assuming they are, what you might gain in response you lose in acceleration.

Now, aside from wheel size you can also increase a car's responsiveness with adjustable shocks. However, in order to increase acceleration you need to change either gear ratios or increase horse power. So I ask, when selecting wheel size, which would you rather be lacking, responsiveness or acceleration? Which is easier to fix?

 

The other problem with very low profile street tires (ie 215-40-17 for example), is that the sidewalls are made a lot softer than they should be at that height as a compromise towards comfort. A typical 50-55 series r-tire has a stiffer sidewalls than most 35-40 series street tires...

For your relatively low-power application (i'm going by your sig), the best setup would be a 13x8 wheel with 215-50-13 or 235-45-13 Kumho r-tires. Well, actually, the best setup right now would be whatever you have on the car now so you can get your feet wet first. Once you get some decent seat time, THEN go for the 13s with some sticky Kumhos...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Geratol &raquo;</TD></TR><TR><TD CLASS="quote">Here's something to think about:

Some people claim that larger wheels are more "responsive" (I have never noticed), but assuming they are, what you might gain in response you lose in acceleration.

Now, aside from wheel size you can also increase a car's responsiveness with adjustable shocks. However, in order to increase acceleration you need to change either gear ratios or increase horse power. So I ask, when selecting wheel size, which would you rather be lacking, responsiveness or acceleration? Which is easier to fix?</TD></TR></TABLE>

Good point, I didn't think of it in that prespective. Now that I think about my old set of 15's the problem might have been my tires. Even with a set of light weight plus sized wheels I still noticed a difference in take off.

For the sohc it's much easier to fix the responsivness than the acceleration. Also I can find a set of good 15" tires much cheaper than the 17".

Thanks,
Rob

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jsi &raquo;</TD></TR><TR><TD CLASS="quote">The other problem with very low profile street tires (ie 215-40-17 for example), is that the sidewalls are made a lot softer than they should be at that height as a compromise towards comfort. A typical 50-55 series r-tire has a stiffer sidewalls than most 35-40 series street tires...

For your relatively low-power application (i'm going by your sig), the best setup would be a 13x8 wheel with 215-50-13 or 235-45-13 Kumho r-tires. Well, actually, the best setup right now would be whatever you have on the car now so you can get your feet wet first. Once you get some decent seat time, THEN go for the 13s with some sticky Kumhos...
</TD></TR></TABLE>

I am using my stock 14" steelie rims with the stock 185/65/14 tires. I'm pretty used to the feel of the tires but for any agressive street driving the tires loose traction. Would you suggest a 15" tire for the street? I heard the Falken Azenis are a good street/performance tire.

Who makes a 13x8 wheel? Sorry for the questions.

Thanks,
Rob

 

It depends on what class you're going to run in. If you go with 13's only R-Compound tires come in good sizes and 13x8 rims are usually race only. If I were you I would get some 15x6-7.5 (15x7.5 would be ideal) rims with some 205 Falkens on them. It will be a world of difference compared to your 14x(5.5 I would guess) and stock 185 junkers.

 

I agree with Geratol and pretty much everybody else. 15's with good tires (205/50 and wider) will be just as grippy and faster than 17's, especially with a relatively sedate engine package. 17's would allow bigger brakes for a serious road racing setup, but that is the only advantage I can see IMHO.

Geratol- Do you run 15x7.5 rims without rubbing problems? With what offset? Did you have to roll your fenders at all? Perhaps no problems at all?

 

When not on 13x7.5 for racing I use 15x7.5 wheels +38 offset. I had to roll the fenders lightly to prevent rubbing. Other then that it's a perfect fit.

 

Excellent. Thanks again. Do you still run a 45 to 50 aspect ratio on the 13x7.5 to shorten your gearing? I'm also more than a little curious about that trick co-axial rear sway you have.

Sorry for the questions, but..... nobody expects the Spanish Inquisition!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by thirdvector &raquo;</TD></TR><TR><TD CLASS="quote">Excellent. Thanks again. Do you still run a 45 to 50 aspect ratio on the 13x7.5 to shorten your gearing?</TD></TR></TABLE>

I used to use the 235/45/13 but I found out that the newer K6A compound only comes in the 215/50/13 so I switched. The newer compound stays sticky like new for much longer then the older K8A compound. Even though I lose some tire width and a smige of gearing it's worth it for the stickier rubber. Eventually I will switch back to the 235 when it's available in the K6A compound.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by thirdvector &raquo;</TD></TR><TR><TD CLASS="quote">I'm also more than a little curious about that trick co-axial rear sway you have.
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What does this mean?

 

bigger is better in many ways. in unlimited racing, they will use large dia. rims, but *only* because to get the biggest brakes in there. for example, top production car racing that still resemble street cars is/was BTCC (which i haven't followed to closely in the last few years) but they were running 19". and one main reason was because to large brakes. there was also something about stability, i'll have to dig into some old mags to find out.

f1 runs 13" rims, but only because the rules said so. if te rules allowed bigger rims they would go up in size no doubt.

in cars such as EF/Ek/EG/DC ... etc. you should only get as big as your braking clearance needs to be. so with stock brakes, 15", or actually 14's is the best. smaller rims will have lower polar moment (most notable would be during a launch where there is drastic wheel speed change; under normal driving the wheel speed doens't change that much so polar moment while nice, doesn't mean a whole lot in this case). but really, it's not something you'll really feel since wheel is so free spinning anyway.

i have experienced a lot of things when it comes to tracking cars, and i can say i can feel the wheel weight difference and dia. when tracking, but the actual lap time difference is small.

 

can i try some of that new compound?? *wink*

you need to buy my 13x9's foo!

 

Frank,

I agree with you about the bigger rims when it comes to other forms of racing but within the rules and format of autocrossing it just isn't a good idea.

Now if we are talking about road courses, custom fender pannels, unrestricted gears, and 300whp, then I would start looking at the biggest f'n wheel that I could fit on the car.

BTW who said your 13x9s are for sale! IM me if it's true.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Geratol &raquo;</TD></TR><TR><TD CLASS="quote">

I used to use the 235/45/13 but I found out that the newer K6A compound only comes in the 215/50/13 so I switched. The newer compound stays sticky like new for much longer then the older K8A compound. Even though I lose some tire width and a smige of gearing it's worth it for the stickier rubber. Eventually I will switch back to the 235 when it's available in the K6A compound.

What does this mean?</TD></TR></TABLE>

I've seen you post the above comment a few times, so i though i'd let you know that we got some 235-45-13s in April and the ARE the K6A compound. Talon Tire did not have them in stock and they were ordered in March i think. Just FYI as I though this info would be usefull to you and others...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GhettoRacer &raquo;</TD></TR><TR><TD CLASS="quote">bigger is better in many ways. in unlimited racing, they will use large dia. rims, but *only* because to get the biggest brakes in there. for example, top production car racing that still resemble street cars is/was BTCC (which i haven't followed to closely in the last few years) but they were running 19". and one main reason was because to large brakes. there was also something about stability, i'll have to dig into some old mags to find out.

f1 runs 13" rims, but only because the rules said so. if te rules allowed bigger rims they would go up in size no doubt.

in cars such as EF/Ek/EG/DC ... etc. you should only get as big as your braking clearance needs to be. so with stock brakes, 15", or actually 14's is the best. smaller rims will have lower polar moment (most notable would be during a launch where there is drastic wheel speed change; under normal driving the wheel speed doens't change that much so polar moment while nice, doesn't mean a whole lot in this case). but really, it's not something you'll really feel since wheel is so free spinning anyway.

i have experienced a lot of things when it comes to tracking cars, and i can say i can feel the wheel weight difference and dia. when tracking, but the actual lap time difference is small.
</TD></TR></TABLE>

Cool, thanks for the long post.

I'm not going to be attending lots of track days but would like some extra grip for daily driving and weekend outings. From what I gathers here from the experienced guys I'll search around for a good set of 15's and mid priced tires.

Thanks,
Rob

 

ahh i didn't read the original poster's post in detail. if specifically for autox, then the widest and shorterest tire would be ideal! and that means 13x9's would be just about the ultimate setup for EF/EG/EK and DA/DC chassis.

if on budget, get a set of those 13x7.5 axis like jeremy has or good 13x8 or 13x9 if one can afford the extra cost. but those are not recommend for street duty. for good dual purpose, some 15x7 would be good. and 14x7 if somebody ever start to make 'em.

 

Holy Fawk! 235s in a K6A!

Could you please let me know what the date stamp on them is? I just ordered 2 new 215s for nationals