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      09-23-2020, 09:25 PM   #1
Robbyjai
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245 Fronts 275 Rears

Hi Guys

I am hoping someone with a bit more knowledge and experience might be able to answer this question ...

A bit about my set up...

i recently got a BMW M2C. I've got the BMW 763M wheels on my car with the 6 Piston M performance BBK ..

Wheels - 19x9 Fronts and 19x9.5 rears.
Tires - 245x35 Front and 265x35 rears
Currently running the Micheling Pilot Cup2

I track my pervious cars a lot however my knowledge is based on an AWD car and its inherent nature and tuning accordingly.

The challenge I have is choices of 19" Semi Slicks are a bit limited here in Australia.

I have found a semi slick compound I like but I can only get either one of the following set ups

Option 1
Rims - Same as above (19inches)
Tires - 265x35 (F) and 275x35 (R) an almost square set up

Option 2
Rims - Same as above (19inches)
Tires - 245x35 (F) and 275x35 (R) an almost square set up

Now my question is ... should i go the Option 1 set up... or Option 2...

The car as most of you know has a tendency to over steer and spin up the rear wheels.

My Car is still stock except for stage 1 Tune. I intend to do modifications bit by bit to get some reference time laps per mod to see the effect of each modification and improvements

I am leaning towards option 2 as I suspect that will help me dial out some of the over steer tendency (will do suspension mods later)


Can anyone shed any light on whether they think option 1 or 2 is better and why

looking for people who have this set up or have experience in this type of set up for an RWD Car as my experience is in AWD Cars

thanks
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      09-23-2020, 11:03 PM   #2
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All my track experience is in RWD cars, but I drive with the local Audi Club quite a bit and have watched several friends adjust from AWD to RWD over the last few years.

You can’t get on the throttle as eagerly and early in RWD as you’ve been able to get away with in your AWD cars. It feels slow to be patient with throttle until you have the steering wheel pointed more or less straight ahead, but that’s part of the learning curve as you transition to RWD, regardless of what tires you’re running.

Are these tires for your 763m wheelset, or is the 9/9.5 wheelset something else you plan to use on track? 763m should be 9/10.

In any case, 265/35 will probably require some massaging of your wheel liners, and is also a bit wider than ideal on a 9" wide wheel, so I’d probably go 245/275 for minimal fuss and better steering response.

From a handling perspective on stock suspension though, I enjoyed square wheels and tires for the improved turn in and mid-corner balance, so could see a good argument for 265/275 getting closer to a more balanced feel.

All that said, semi-slicks only last a few days, so maybe give them both a try and report back.
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      09-24-2020, 03:18 AM   #3
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hey bentom sorry are correct yes 10inchs at the back wheel not 9.5 my bad.

and yes agree with you on a more square set up hence my line of thinking around the 265 and 275 rears

curious to see if anyone on this forum has run 265 at the front before thats all
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      09-24-2020, 04:51 AM   #4
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Car will certainly transition a bit towards understeer with 245/275 setup, so I think I’d depends on your feeling with stock tire sizes. If you feel the car is too tail happy. Extra rubber in the back will help keep the tail planted just a bit more.

If you like a “loose” feeling car then closer to square will tend towards that feeling more. This setup will likely require using throttle the transfer the weight to the back on corner entry oversteer, and you’ll need to be ready to correct steering on corner exit under partial throttle. The active diff helps out a lot in this situation already though.
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      09-24-2020, 07:19 AM   #5
Robbyjai
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thanks for the input thats what i suspected.. im use to dealing with understeer and trail braking into corners...and the M2 is very tail happy ... and i want to dial it out a little bit ... so it seems the 245/275 might be suitable
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      09-24-2020, 10:01 AM   #6
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Quote:
Originally Posted by Robbyjai View Post
thanks for the input thats what i suspected.. im use to dealing with understeer and trail braking into corners...and the M2 is very tail happy ... and i want to dial it out a little bit ... so it seems the 245/275 might be suitable
Kankles is runing option 1 (on 437s same dimension spec though) and he is lowered on camber plates. There is quite a bit of rub up front with parts of the fender liner gone.

Tires wouldn't hapen to be Federal 595 Pro whatevers?

I came from a MK3 Focus RS and it took me a while to adapt my driving style. M2C is more of a slow in fast out car than an AWD car. The extra power wont be doing you any favours in learning how to modulate the power. If you have boot mode I would adjust the TQ by gear to a point where you dont overload the rear tires.

Another option is 265/35 all around, then you can have your tires rotated to extend their life a bit and it should have a more neutral atitude.

Also I would get an alignment if its never had one. Rear toe seems to affect oversteer a lot on these cars.
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      09-24-2020, 12:37 PM   #7
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Quote:
Originally Posted by Megator View Post
Quote:
Originally Posted by Robbyjai View Post
thanks for the input thats what i suspected.. im use to dealing with understeer and trail braking into corners...and the M2 is very tail happy ... and i want to dial it out a little bit ... so it seems the 245/275 might be suitable
Kankles is runing option 1 (on 437s same dimension spec though) and he is lowered on camber plates. There is quite a bit of rub up front with parts of the fender liner gone.

Tires wouldn't hapen to be Federal 595 Pro whatevers?

I came from a MK3 Focus RS and it took me a while to adapt my driving style. M2C is more of a slow in fast out car than an AWD car. The extra power wont be doing you any favours in learning how to modulate the power. If you have boot mode I would adjust the TQ by gear to a point where you dont overload the rear tires.

Another option is 265/35 all around, then you can have your tires rotated to extend their life a bit and it should have a more neutral atitude.

Also I would get an alignment if its never had one. Rear toe seems to affect oversteer a lot on these cars.
Suggest using 265/35 and 285/35 tires on those rims. I have run 265/275 PS4s and 255/285 RE71Rs.
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      09-24-2020, 01:10 PM   #8
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Quote:
Originally Posted by landapanda View Post
Suggest using 265/35 and 285/35 tires on those rims. I have run 265/275 PS4s and 255/285 RE71Rs.
Thats what I run on 18s . OP has the 2NH option so has to have 19"s from what I remember 285/35/19 is a rare tire size for semi-slicks.

Also the Federals are very very wide for their indicated size, so ymmv.
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      09-24-2020, 05:43 PM   #9
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Quote:
Originally Posted by Robbyjai View Post
thanks for the input thats what i suspected.. im use to dealing with understeer and trail braking into corners...and the M2 is very tail happy ... and i want to dial it out a little bit ... so it seems the 245/275 might be suitable
My question is WHERE is it tail happy?

* Corner Entry to Apex
* Apex
* Apex to track out

I suspect your talking about TTO (trailing throttle oversteer) which of course is apex to track out.

Our cars have lots of TTO :-) Especially if your experience is coming from a AWD platform.

One of the common topics is putting as much tire on the rear rims as you can. This helps with TTO and taking additional advantage of the M Diff. Its a fine balancing act with rim width, suspension setup, tire selection and driver style.

What are your tire options for DOT R Compounds?

Hoosiers, Toyo's, Federal's, Nitto's, BFG R1's, Michelin Cups, Nanking? Hankook, Pirelli?
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      09-24-2020, 09:37 PM   #10
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thanks all for your input and Seat Time Rules yeh pretty much what you described. I'm used to relying on all wheel drive to scrabble out of corners so i can get on the throttle earlier...its just reprogramming my brain to how RWD Biased cars drive.. having said that.... i was able to reprogram my brain pretty quickly and ended up posting the 4th fastest time of the day in the sprint formats out of 50 cars and my car is bone stock and a whole bunch of other modified cars.....so i did come to grips with the car pretty quickly

its just i feel with more power rear wheel traction will be an issue.

In australia our choices of R Compound Semi Slicks is pretty limited right now... and in the tire sizes i want.. I can either stay with the Michelin Cup 2s 245/265 combo... and up it to a 255/275 combo....... or go another brand which i have used before and i rate quite well which is the nanking AR-1 which I really like more

the cup 2s are great... but just a personal preference i like the AR1 more. So i have decided on option 2 which is 245 Fronts and 275 Rears to get a slightly bit more understeer Bias and then will use coil overs and suspension tuning to dial in the bias to my personal preference

i also did some further research and interestingly enough ... the tyre reviewer guy in the UK addressed this very question and concluded the combo he has recommended (255F & 285R) is pretty much the same combo ratio i am going for which is 245F & 275R .. i know its not quite that simple but yeh roughly there abouts


for those interested in the video here it is
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      09-26-2020, 02:26 PM   #11
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If you want maximum mechanical grip form the Nanking's you will need at least 3 degrees of Neg camber up front. IMHO probably closer to 3.25. Buy some camber plates you can run with the stock struts.

It will balance the car, turn in will be much crisper, and the biggest bonus will be even tire wear. Which on a staggered setup is a huge advantage.

My $.02
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      09-26-2020, 11:15 PM   #12
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Personally I'd go as wide as you can up front. More front end grip - better turn in - better rotation - you can get back on the power earlier. I found 275 with 200TW to be plenty of grip on the rear of a stock power M2C.
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      09-27-2020, 10:07 AM   #13
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I don't quite understand the logic of running 245/275 will net you more rear traction considering the 265/275 setup has the same rear rubber!

265/275 will be faster than 245/275, period. Shorter braking distance and less understeer is the pros of running 265 front.

You have a stage 1 tune so that really doesn't help with the corner exit oversteer on track. On the street that power level is pretty much useless you have at least 305 rear.

IMHO you better off selling those 763 wheels and get wider Apex wheels 9.5/10.5 and run 275/30 & 305/30 19. If you don't have the optional BBK than go back to 18 and run 275/295.

R tyres have a lot more sizes in 275 & 305 19

Last edited by Karmic Man; 09-27-2020 at 10:13 AM..
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      09-28-2020, 01:49 AM   #14
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Quote:
Originally Posted by Montaver View Post
Personally I'd go as wide as you can up front. More front end grip - better turn in - better rotation - you can get back on the power earlier. I found 275 with 200TW to be plenty of grip on the rear of a stock power M2C.
ok thanks. im hearing a bit of a mixed bag of responses. so i think i might have to experiement and try both set up see which works

im more worried about rubbing if i stick 265 at the front
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