85 replies to this topic

[squareback]

but just a question...lets say same wheel you described as above 15lb 13's and 15lb 17s..when turning and lets say you load in the front corner at 1000 pounds(theoretically) wont that larger diameter wheel/tire absorb or disperse more of that energy throughout the larger area causing less understeer than a 13" that the force/energy is more concentrated in a smaller area??

<{POST_SNAPBACK}>

Not really, since most of that engery is put into the actual contact patch, which we already established is exactly the same for both tires (same wheel width, same tire width, same aspect ratio). If push comes to shove, I suppose the 17 would disperse it a bit better since it can spread it through the larger amount of material in that tire, but the difference would be so small that I can't imagine it would be noticeable.

Mike

[strudel]

and no original mini coopers do not fly like rockets LOL.. my dads friend has one.a 1978 1100cc single su carbed.. it feels like it does but it is definately slow! and it has bodyroll like hell..its not modded though..!!! the fast ones are heavily modded and usually run 13" wheels as they can go no larger.. .. but we in our rexes can...

I just want to add some information to this comment. I have a Mini. And many Mini owners today are getting rid of the original "A" series engine and putting in a nice B16 VTEC and running anything from 10's to 15's for rim size. I had the pleasure of riding in one with 13" rim/tire combo on a racetrack in Germany and that particular Mini beat the Porsches and BMW's on the course.

Just a comment on rim/tire combos. With plus sizing today one can retain the original diameter/circumference of an oem 13' and convert to a 15 or 16 with a minimal change in speedometer reading. Now if the weight of the rim/tire combo can be kept within a similar tolerance what would change? Possible the wider track might help cornering but the straight line accereration should be similar or not? That is my question. Have at me! JS

[RARECRX]

everyone has great theory's... now we need someone to test this stuff out LOL... I might just do it with my g-tech pro LOL.....17" 205/50 against 13" 205/50 if i can find the same brand tire for both which will be next to impossible LOL.. I think the load dispertion has more affect than we think ..

Edited by etmydst, 15 February 2006 - 06:23 PM.

[1stGenRex]

i just got 16's on my car and it feels great...

[slavteren]

i can only tribute with my own experiense:

175/50-13 has absolutely NOT enough grip. once up in speed they are great, but when you need to put the power to the ground it sucks

185/60-14 good comfy tire, a litle better grip then the 13's but less presision.

195/45-15 really good tire, just the right presision, and way better acc then the 2 others.

195/50-15 as obove, just a litle more comfy, marginal worse presision.

215/40-16 this is the ultimate streettire i has been driving. comfort as the 195/45 and almost endless grip.

205/40-17 this is just for looks.. but i use them on my civic anyway really uncomfy, and way to many downsides contra the grip-

215/40-17 like the 215/40-16 but a bit slower on acc. this actually is a good daily tyre for the rex, it makes the dirving a litle more civiliced, and the higher gearing helps me to compensate for the bit low gearing of the cz.


and by the way you CAN NOT compare a streettyre and a racetyre, they are 2 diff types of tyres, and the only thing they have in common is that they are made of rubber...

[Airgazm86]

the only thing that the diameter of a wheel will do for hadling is allow for more tire options and hence wider tires.....my point is that in straight line accel and decel, a smaller wheel is better. but you could say that the faster accel makes more torque stear and that will effect handling. but this is not my point....again, just accel and decel!

<{POST_SNAPBACK}>

Tranny gearing plays a big part in choosing tire sizes. My DSM has a 4.94 fd and 1st geat is basically useless with stock tires. I couldn't imagine running anything smaller.

Weight is another factor to consider. We're mostly talking about ~2000 lb. cars...sure you're 175/70/13s may feel good on your Rex. But consider running the same tire size on a ~3000 lb. car...they probably will feel like jello.

Wide, low-profile 13" tires are expensive when bought new and few street tires exist in these sizes...prove me wrong. Most people asking about which street tires are best are probably running 13x5" wheels, which probably won't fit a 205 tire.

Last but not least, most modern cars will have trouble fitting 13s because of brake size.

And just to play devil's advocate, why don't JGTC, BTCC, WRC, etc. cars run 13s if they are the ultimate in performance? Probably brakes, but who knows.

Who on this forum supporting 13s with huge, sticky race tires actually runs 13s on the street?

I'll choose aesthetics over physics any day of the week. My car looks absolutely rediculous with 13s or 14s because I've tried it.

[kakabox]

Just a comment on rim/tire combos. With plus sizing today one can retain the original diameter/circumference of an oem 13' and convert to a 15 or 16 with a minimal change in speedometer reading. Now if the weight of the rim/tire combo can be kept within a similar tolerance what would change? Possible the wider track might help cornering but the straight line accereration should be similar or not? That is my question. Have at me! JS

<{POST_SNAPBACK}>

Yes, if the rolling diameter and wt of the plus size tire/wheel combo remains the same as the oem, then in theory, the acceleration should be the same.

The main thing I got from reading the article is that, duh, as you increase the contact patch your ax times get better. But, note that as they got into 16" and 17" wheels and tires and the wt of the combo increased, the accel was noticable slower. That's the increased rotational inertia (the flywheel effect) of the heavier wheels/tires coming into play. The ax times got better due to the increased contact patch and shorter sidewalls allowing the turns to taken at a higher speed; essentially being able to carry more speed through the entire course, hence, quicker times.

Oh, btw, imo, I'd listen to what squareback's laying down, it's right on.

Cheers!

[Surestick]

I planned to post this earlier (about 2 pages ago) but I was at work & the internet went down so forgive me if I'm repeating something already said.


I think that what a lot of people here are arguing is that the test is far from scientific.
They should have tested the same make/ model/width of tires in two different sizes & kept everything else equal (even down to rim make/model/width).

The tests should have measured G's on a skidpad, quarter mile times & distance to stop from a set speed, anything else is subjective.

If you really want to get anal you should repeat the tests on different road surfaces - the Quebec roads I drive on are much worse than the Ontario roads 100km away, maybe a tire with more give in it will give me better ultimate grip on my roads than someone with the same car in Ontario or if I'm using my car on a smooth racetrack.

Just because something feels faster or I could drive it around a track faster the first time I try it doesn't mean it is faster. I could set the damping on my shocks to max put in really stiff sway bars and my car will feel faster but it won't be.

I could practice driving a car on a track for weeks with one set of tires & get to know how they feel at the limit & exactly what they can & can't do (or at least I could if I was a racing god...). My first few times out on a different, grippier, set-up I might be slower if they feel to me like they are about to let go all the time. Until I get used to them I will be slower.

Also, don't forget suspension set-up. If you change the weight of the rim/tire you are changing the forces the suspension has to control & might be faster with re-adjusted suspension.


Man - you certainly started a lively discussion!

Edited by Surestick, 15 February 2006 - 06:56 PM.

[kakabox]

.....17" 205/50 against 13" 205/50 if i can find the same brand tire for both which will be next to impossible LOL.. I think the load dispertion has more affect than we think ..

<{POST_SNAPBACK}>

No, the load "dispertion" has nothing to do w/this comparison. Even if you were able to find a 205/50 13 tire/wheel combo that weighed EXACTLY the SAME as the 205/50 17 tire/wheel, the lower gearing created by the 13" wheel & tire's 21.1" Rolling Diameter vs. the 25.1" RD of the 17" combo would accelerate you quicker.

Not to mention, that, w/the 17" wheel, most of the mass (the tire) is placed further out from the center of rotation when compared to the 13" combo, hence, the 17" combo would have more rotational inertia...more rotational inertia, more energy required to accelerate the wheel/tire.

No, given an apples-to-apples comparison based on the above, on an ax course, I'd put my money on the 13" wheel/tire combo.

Edited by kakabox, 15 February 2006 - 07:53 PM.

[RARECRX]

hate me .. but ill be an outcast and go with the 17's.. this is a great discussion ..without discussions and opposing opinions we wouldnt have the basis for theorys to be proven... what a great opinionated post...havent seen one of these for awhile lOL...

[mep]

I just wanted to add that you keep using the 205/50-13 vs. 205/50-17 comparison... that is completely pointless. No one would be able to fit 205/50-17s on a CRX regardless.

For the record, a good comparison that is actually feasible for our cars, for back to back testing would be:

205/60-13 vs. 205/40/17 or 215/50-13 vs. 215/40-17...

I'll take your $100 bet all day long & raise you $10-grand that the 13s will crush the 17s in every area of performance. I'm talking equal street tires, not street vs. R-compound. Just like Scott & Mike have been drilling over & over, physics is what it is

I have used all derivitives of tire sizes from 13-19" on countless 1,2,3,4,5,6 & 7th-gen Civics & CRXs over the years, plus a Prepared Miata, two MR2s, SE-R Sentra, Saab 900, G20, & even a couple of Mustangs. There's no way to match the gearing advantage of smaller wheels with larger diameter wheels for regular spirited street driving. If you're talking about 100% testing limits of suspension, braking, etc... then the argument is no longer valid, since that type of comparison should ONLY be exhibited at a sanctioned event, so the R-compounds certainly do come into play... & even so, comparing R-compound 13" as lesser than R-compound 16-17" on a 1st-gen CR-X, is still the same losing argument.

This post is meant as a friendly discussion BTW... !

*edit... I could have summarized all of my thoughts as "stock diameter or 2-3% smaller is the best bet for every aspect of performance, other than all out top end speed

Edited by mep, 15 February 2006 - 08:24 PM.

[Screech]

I'm done reading. Not considering non dot tires/or dot slicks I have to agree with Etmydst if proper plus one sizing is used. And I believe this was the point of the article.

Stock my car has 175/70r13 ( just like a lot of yours ), currently I run 205/40r16. Overall 16s are shorter, smaller diameter, less circumference. Theoretically I gain gearing advantage. I say theoretically because the difference is <1%. But, I do gain contact area, and cornering feedback/response. I can brake harder, go faster though a corner and accel harder coming out. I doubt that the placement of the extra weight to the outer area of the radius is enough to negate the advantages I have gained.

Another thing, not all street tires are created equal, duh right. Brand x's model 1 275/60r15s may have a foot print with of 10 while Brand y's model 5 275/60r15 may have a foot print with only 9.25. In other words 275 is the section width, not what’s on the ground.

I've seen several post where people are stating that they larger rims require more energy/force to accel/brake because they are bigger. They are not looking at proper plus sizing. When proper plus sizing is used the overall diameter change is <2% (my 16s have ~.83% smaller diameter than stock). In this case the RIGHT answer to why more energy/force is the placement of the weight on the radius, while this was stated several post following it prove that not everyone understands this.

FORGET straight lines. To drive only in a straight line indicates in it self to not be street use. Straight line drivers want a lot of sidewall to flex so that at low pressure they get a "square" foot print out of that 15-16" wide slick. For those confused: 6-7x15" area of rubber on the ground > 1-2x15" on the ground. But, as you have seen when they need to steer for what ever reason they get VERY squirrelly.

Italic = changes made to original post

Edited by Screech, 16 February 2006 - 12:25 AM.

[strudel]

A good elaboration on what I said earlier. JS

[mayhem019]

Just wanted to say that if you have a larger overall diameter tire then you effectively have a larger "footprint" so you should also be getting more traction that way - not just by the width. I think that part is overlooked sometimes

Yes some acceleration is lost with larger tires, but you should be able to brake harder before they lock up (this is assuming widths are the same)

Edited by mayhem019, 16 February 2006 - 01:31 AM.

[mep]

if proper plus one sizing is used.

<{POST_SNAPBACK}>

This is the key point of the discussion, & the key point of my argument. There is no proper plus sizing for 17s on a 1g/3g...

175/70-13 = 22.6" diameter
185/60-14 = 22.7"

205/40-17 = 23.5"
205/45-17 = 24.3"
205/50-17 = 25.1" (!!)
215/40-17 = 23.8"

That's over 3% difference in diameter between the stock sizes, & the smallest 17" tire on the market. No matter how you measure it, it will take more force to turn & stop a larger rolling diameter.

Proper plus sizing for a 1g/3g(within 1% difference of factory diameter):

205/60-13 = 22.7" diameter (plus zero)
205/55-14 = 22.9" (plus one)
195/50-15 = 22.7" (plus two)
215/45-15 = 22.6" (plus two)
195/45-16 = 22.9" (plus three)
215/40-16 = 22.8" (plus three)

Some under-sized examples that will regear for quicker acceleration, increased steering response, & shorter braking distances:

185/60-13 = 21.7"
195/60-13 = 22.2"
215/50-13 = 21.5"
225/45-13 = 21.0"
225/50-13 = 21.9"
195/55-14 = 22.4"
195/45-15 = 21.9"
205/40-16 = 22.5"

*BTW, I love all of this tire talk...