Another tire question ...

[LOUCFUR]

Im currently using my stock wheels with r compounds to autoX. I'm gonna get a LSD installed next month. But i was thinking of buying wider wheels and tires to help me w/ traction ... Currently I have 225/45/17. And I was thinking of getting some 17x8 wheels. And by some of the old threads I've seen. It seems the widest tire I can fit would be 245/45/17. ... Now, my dd tires r 235/40/18. And it seems like if I go any wider, I'll be rubbing.

So my question is, would it be worth buying a set of 235 r compounds? Or should I just keep what I have ...

[BlaineWasHere]

you'd want to run 245/40/17. 245/45/17 is too tall of a tire.

I run 245/40/17 on 17x8 wheels et45.

[LOUCFUR]

Yeah, I meant 40. And what does et45 mean? ... My current setup (Komi yellow and neuspeed springs), it seems like 245 would rub.

[BlaineWasHere]

the offset of the wheels

[LOUCFUR]

Idk if I'll be able to fit the 245. would I feel a difference with the 235?

[BlaineWasHere]

How do you know they won't fit you didn't even know what I was talking about when I listed the off-set which is an important measurement for wheel and tire fitment.

I used to run 245's when I just had springs.

[LOUCFUR]

true^ ... im was just looking at the side of the car. and it seems theres no more room ...

[BlaineWasHere]

Honestly unless you are really trying to "win" you're not going to see much difference from 235 to 245.

You're young and you should just be spending time worrying about ways to make your driving better, not your car.

[LOUCFUR]

Thx ... During the off season, I'm also gonna work on my driving skills. I plan on going to the go karts every wk or every other wk. To work on my race line ...

I actually did ok on my 1st yr. I finished 2nd outta 28 drivers in my class ... But the guy that won the championship. Was always 4 secs faster than me. That's y I want to improve my car and driving skills ...

[LOUCFUR]

.

[LOUCFUR]

bump to my thread ... i was going through some old threads and i saw this (http://golfmkv.com/forums/showthread...t=drag+radials) ...

the op was using 245/45/17 on classix. and i believe the theyre 17x7.5 ... so do you guys think i'll have any issues if i try to fit 245 on my classix? or should i just get the 17x8 instead? ...

would that give me issues with the sidewall?

[GodSquadMandrake]

Best answer I can give. From here:

Originally Posted by Howard Coleman

F1 in HD.... lessons in plain sight

i'd prefer this thread not turn into an F1 thread but i was watching Spain Qualifying and some items jumped out at me that i thought would add something to the FD-world.

my first year of road racing was in open wheel formula cars and i still remember how neat it was to be able to see the tires work. (it was also really easy to place the tire exactly on the inside apex of the corner).

w the onboard F1 cameras, especially in HD, you can really really see the tires work.

first off, if you see shots of the cars it is clear they are running around a degree plus of negative camber in the front and almost no camber in the rear. this squares w my suggested setup.

from onboard you can watch the tire work thru a corner. you can see that the outside tire as the car turns in has a primary working surface that starts at the inside of the tire's lateral contact and then travels across toward the outer section as the corner progresses. really neat to watch.

a major diff between F1 and FD is downforce. since they develop a lot of it the spring's function is entirely different. it's primary function is to resist ride height change in the face of multiple Gs of downforce.

the FD spring's primary job is to provide a max of 2 inches (at the wheel) of bump travel.

back to F1...at high speed going straight the front tires are making more contact on the inner 1/3 producing less drag. (not to say the outers aren't making contact, just less pressure outer)

note that tire warmers are key. the cars go out and make immediate hot laps in qualifying. if your tires aren't up to temp you are going to go slow. (it generally takes 2 laps to get up to temp w an FD)

i use tire softener and that makes the tire sticky in the first lap (wears off at the end of lap 2 but by then the tires are up to temp)

so don't expect to go fast on laps 1 and part of 2.

note how the tire contact width is exactly the same as the rim width. you don't want tires bigger than your wheel...

i run 255s w 9.5 fr and 295 10.5 rear

one of the qualifiers was understeering in Q1. F1 prohibits setup changes BUT allows tire pressure adjustments. so in the rarified Tech-air of F1 what did they do? took some air out of the front tires.

speaking of tire pressures...

i was at Road America w a friend a couple of weeks ago. it was 55 degrees. i brought my air pressure gauge and pyrometer.

by adjusting (lowering) his tire pressures (over 10 psi) over a few sessions we had him running 20 seconds (4 mile track) a lap faster and he remarked the car was easier to drive.

ah, lowly tire pressures really are King.

his tire temps averaged 103 degrees so there is alot more speed to be had as summer arrives.

the pyrometer will tell you not only camber, toe, spring. swaybar info (actually EVERYTHING) but will tell you if a tire should have more or less air pressure. you are blind without a pyrometer and pressure gauge.

i invite anyone to post their tire temps and pressures and we can do some tweaking together.

BTW, as someone who turned off F1 15 years ago due to a lack of racing/PASSING i suggest you take a look this year. i happened to bump into the Turkish GP a few weeks ago and was blown away. a very very racey race w lots of passing. it appears they have solved their problem and are back to racing.

howard

The second half:

Originally Posted by Howard Coleman

bumped into an interesting article in Grassroots Motorsports this month...

don't you just hate it when someone ACTUALLY TESTS THEORIES?

light wheels V heavy

fat tires V thinner tires.

the executive summary was

maybe lighter wheels are good for the slightest of advantage.

tires w contact patches larger than the rim width are SLOWER and HARDER TO DRIVE.

as you may remember my post one suggests run tires w a contact patch no larger than rim width. (i also mentioned this in my above post in relations to F1.... but what do they know.)

the speed differential between fatter tires and tires the width of the rim was quite a bit in racing metrics.... 53.65 seconds V 53.13.

wheel was 17 X 9

tires were 245 40 and 255 40
contact patch was 8.8 and 9.1

"The narrower and shorter 245 tires felt more nimble, allowing both drivers to place the car closer to the cones with complete confidence. Turn-in was sharp, acceleration felt noticeably better, and when it came time to throw out the anchor, the car felt as if it slowed more quickly. It seemed the narrower tires simply offered more precision and communication.

In comparison, the wider tires felt a little lethargic in quick transitions. They also had an elastic feel when accelerating away from faster corners, often transitioning to gentle power-on oversteer as rear end breakaway was hard to anticipate." GRM


key words from above:

precision
communication

i would add linearity and you have what you need to go fast.

i run a 9.5 rim in the front w a 9.1 tread width.

i run 10.5 rear w 10.6 t w.

don't go too big for your rim width or you will be doing the elastic fantastic.

howard

[LOUCFUR]

Awesome ... Thx for the post ^ ...

[bostonaudi]

I like the feel of 225-45-17's with r-comps, as above, they accelerate better and feel more nimble than the 245-40-17's I normally run. For r comps I run the stock size, when running Direzza's I do the 245-40's. I haven't done back to back lap times, but I suspect the 225-45's in a r-comp would be slightly faster as they feel that way. They have less drag on the straights too.

[LOUCFUR]

Originally Posted by bostonaudi

I like the feel of 225-45-17's with r-comps, as above, they accelerate better and feel more nimble than the 245-40-17's I normally run. For r comps I run the stock size, when running Direzza's I do the 245-40's. I haven't done back to back lap times, but I suspect the 225-45's in a r-comp would be slightly faster as they feel that way. They have less drag on the straights too.

off the line they fell good. it just feels like im sliding on the turns ... hopefully the lsd will help me on that ...

[TDICup902]

Would running a 225-40-17 possibly help out with the sliding issue you're feeling? Cause a 45 height tire would have a little more give in the sidewall area than the 40 height tire. This year I will be running a 235/40/17 Toyo R888 on 17x8 wheel. I will have to measure and see what my actual contact patch would be.

[GodSquadMandrake]

Hahaha when aren't we sliding in turns? I love it when people talk about how such and such car "drives on rails" or these tires have "endless grip". When it's really more like "I dropped 2 seconds off my lap time with these tires."

[LOUCFUR]

Originally Posted by TDICup902

Would running a 225-40-17 possibly help out with the sliding issue you're feeling? Cause a 45 height tire would have a little more give in the sidewall area than the 40 height tire. This year I will be running a 235/40/17 Toyo R888 on 17x8 wheel. I will have to measure and see what my actual contact patch would be.

my r compounds are 225/40/17...

[bostonaudi]

Originally Posted by TDICup902

Would running a 225-40-17 possibly help out with the sliding issue you're feeling? Cause a 45 height tire would have a little more give in the sidewall area than the 40 height tire. This year I will be running a 235/40/17 Toyo R888 on 17x8 wheel. I will have to measure and see what my actual contact patch would be.

a 225-40-17 is way too small, even 235-40 is quite a bit under stock size, I'd go 245-40 or use stock 224-45-17.

R comps have extremely stiff sidewalls - you will have no issues with sidewall flex with a 225-45-17. This is the size many of the compact cars in the ST class in Grand Am run (including GTI). If the car is going sideways, slow down or get better tires, LSD etc.

[TDICup902]

Originally Posted by bostonaudi

a 225-40-17 is way too small, even 235-40 is quite a bit under stock size, I'd go 245-40 or use stock 224-45-17.

R comps have extremely stiff sidewalls - you will have no issues with sidewall flex with a 225-45-17. This is the size many of the compact cars in the ST class in Grand Am run (including GTI). If the car is going sideways, slow down or get better tires, LSD etc.

Hmm that is something to keep in mind. I am just getting into auto cross and tracking. I managed to score a really great deal on the wheel and tires so I couldn't pass it up. I will run these out until they are done this year.

Next year I will be looking into star specs, so I will not have to worry about constantly keeping the heat in the R compounds.

[LOUCFUR]

Originally Posted by bostonaudi

a 225-40-17 is way too small, even 235-40 is quite a bit under stock size, I'd go 245-40 or use stock 224-45-17.

R comps have extremely stiff sidewalls - you will have no issues with sidewall flex with a 225-45-17. This is the size many of the compact cars in the ST class in Grand Am run (including GTI). If the car is going sideways, slow down or get better tires, LSD etc.

So even if I get wider tires/wheels, it's probably gonna go sideways Bcuz I'm still not a good driver ...

Ive talk to 2 other members in this forum and they said that 45 was to big. To go w/ 40 instead ...

[bostonaudi]

Originally Posted by LOUCFUR

So even if I get wider tires/wheels, it's probably gonna go sideways Bcuz I'm still not a good driver ...

Ive talk to 2 other members in this forum and they said that 45 was to big. To go w/ 40 instead ...

225-45-17 or 225-40-18's are the factory sizes, anything else on GTI is not. However most of us have found 245-40-17's to work well on 17x8 rims.

Going sideways can lead to trouble or crashed car.