MR2 Roadster Owners Club

The Workshop => Performance Related => Topic started by: Anonymous on November 4, 2005, 15:35

Title: TYRE Sises: Difference between 00 on 15s and 03's on 15/16s
Post by: Anonymous on November 4, 2005, 15:35
Hi,

Just wondering. I have a 00 which came on standard 15"s, wasn't to keen on the look of them and then changed to 17"s with low profile tyres. However not sure, the car feels slightly understeery on them. i know the 03 Cars came with 15"s on front and 16" reers. Does this set up help and if so was there any other suspension up grade differences between the earlier and later versions.

Not Sure if the difference is only in my head, I only had the car about 3 weeks before I changed the wheels so maybe its just that I'm beging to exploit the car.

Also can anybody tell me how to work out correct tyre pressures. Am running 32 up front and 34 at rears. was running at 30 but ended up ruining a rear that a tyre guy told me was caused by low pressure.
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Post by: Two's Company on November 4, 2005, 20:53
When I was running Bridgestones I found 25f/30r the best compromise.

The understeer is probably due to the front tyres being overinflated.  The handbook figure is 26psi for font.  Officialfigures can be found inside the glovebox.

Hope that helps.
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Post by: Anonymous on November 4, 2005, 22:24
Are these still relevent considering I'm running on 17" rims with tyre sizes 205/40/R17
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Post by: Two's Company on November 4, 2005, 22:28
Erm no...I just need to learn to read the posts properly   s:oops: :oops: s:oops:
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Post by: markiii on November 4, 2005, 22:30
I'm not sure what to advise for pressures on teh same width tyres all round as I've never tried it.

I would say that having teh same tyre width all round is going to make teh it very easy to get the back end out though.

so be careful you don't end up in a ditch.
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Post by: kanujunkie on November 4, 2005, 22:35
i'd be finding a nice big empty car park if i were you, at first anyway
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Post by: Anonymous on November 5, 2005, 09:22
Funny I haven't noticed any oversteer at all (well unless I'm messin around in the Wet) instead I find the car a bit less pointy at the front but like I say this may be because I'm now gettin used to the cars handling. We've had torrential rain here the last two weeks and I even in that I have tons of Grip. But didn't the 00 version run on 15"s all round anyway?
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Post by: Anonymous on November 5, 2005, 09:26
Ok just noticed gapeing oversight, same radias wheels but different tyre widths though, Is this right?
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Post by: Anonymous on November 5, 2005, 11:08
'00 to '02 wheels are 15x6 front and 15x6.5 rear, tires are 185/55/15 front and 205/50/15 rear.
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Post by: aaronjb on November 5, 2005, 11:13
Quote from: "kj"Ok just noticed gapeing oversight, same radias wheels but different tyre widths though, Is this right?

Yep - there's usually a width stagger from front to rear (20mm I think)
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Post by: Anonymous on November 6, 2005, 15:46
I'm guessing this is to make the front end pointier (not sure if I just made that word up!). i'm guessing thats what I'm missing on the corners. But Markiii and Kanujunkie seem to think running the same widths all around will make the car oversteer, whys that. Think they may be wrong though as the rear seems completely planted even in heavy rain.

Can anyone tell me how trye pressures are worked out.
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Post by: dieamond on November 6, 2005, 15:56
I had this problem with my S03 when they were new
195 front
225 rear

I had to use them for like 5000km to have them ok.

After 2 days on track, they are perfect  s:-D :-D s:-D
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Post by: so.simple on November 7, 2005, 13:30
Quote from: "kj"I'm guessing this is to make the front end pointier (not sure if I just made that word up!). i'm guessing thats what I'm missing on the corners. But Markiii and Kanujunkie seem to think running the same widths all around will make the car oversteer, whys that. Think they may be wrong though as the rear seems completely planted even in heavy rain.
I use racing slicks with the same width on the front and on the rear whenever I take the car to a track day. I can guarantee that while the car may seem even better balanced, you will experience some violent snap oversteer if you don't understand and "respect" the car. Be prepared for that.
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Post by: dreambackup on November 7, 2005, 14:10
the stock MR-S understeers. I think you should feel a lot less understeer with wider wheels in front.

I haven't changed my wheel (stock 03) but I made some chassis upgrades and everything help handling and neutrality.

1- harder struts and springs
2- front sway bar
3- breast plate

note that the breast plate didn't take away any understeer but it makes the rear feel more attached to the rest  s:wink: :wink: s:wink:
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Post by: dieamond on November 7, 2005, 14:17
a "MR car" will always understeer at corner entry and oversteer at corner exit

this modification of balance is the trick part of MR driving

but

if you enter a corner with a speed below understeering, you'll generally exit at a speed below oversteer, and in the (small) gap between under and over, it's faster than any other car architecture : that's MR efficiency

plus, understeering allow you to use very late braking when entering the corder, which is another very good point
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Post by: Tem on November 7, 2005, 14:47
Quote from: "dieamond"a "MR car" will always understeer at corner entry and oversteer at corner exit

I'd say that depends a lot from your setup. As an extreme example, say you put two spares at the rear and went driving, I doubt you'd see understeer at all. I believe you'd still have understeer with even tyre sizes all around, cause the nose is lighter. But it is very possible to get rid of it...
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Post by: dieamond on November 7, 2005, 15:24
you would not understeer because the rear tyres would give up very early, but this is not a livable setup

i'm speaking of a MR (MR, NSX, anything, maybe a F1 too) correctly setup, with rear tires according to its power, and front tires accorded to the weight

this car would always understeer at corner entry
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Post by: Tem on November 7, 2005, 21:54
Quote from: "dieamond"correctly setup

this car would always understeer at corner entry

I agree with that. Just wanted to point out that you can change that, so someone doesn't get any ideas of changing the fronts to a very sticky and wide rubber and end up around some pole  s:lol: :lol: s:lol:
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Post by: dieamond on November 8, 2005, 07:06
 s:lol: :lol: s:lol:
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Post by: aaronjb on November 8, 2005, 07:24
Quote from: "Tem"sticky and wide rubber and end up around some pole  s:lol: :lol: s:lol:

It's very sexual in here these days....

*legs it*
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Post by: Anonymous on November 9, 2005, 13:48
So what I'm seeing is perfectly normal than? But what about tyre pressures. When the dealer fitted the alloys and tryes he left them at 30 all around, but a subsequent puncture caused by a screw in the passenger rear highlighted a problem.

When we took the wheel off we found a bump on the rubber. the trye guy thought he could repair this until he seen the the inside of the trye  and the bump had been rubbed away on the inside by the wheel rim. The guy told me this was caused by to low pressure. Im now running 32 up front 35 at the rear. but this is just a knee jerk guess.

Any suggestions considering Im running these tryes all around ( 205/ 40 R17)  s:?: :?: s:?:
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Post by: Anonymous on November 10, 2005, 01:03
Question for the group - 17s seem to be the optimum wheel size (both visually and what will fit in the wheel well), but I've never seen anyone discuss optimum wheel widths with the 17s (front to rear) or a good discussion on optimum tire sizes while running 17s.  Also, what about correct wheel offset?  Should that differ front to rear?  I think most buyers purchase a set of 4 wheels that are identical (and tires too) and maybe that's the wrong way to go.  Plus, what might be the best setup for the street, might be all wrong for the track......... except that I don't drive on a track, as I'm sure most MR2 don't.  As far as under or over steer go, almost all the OEMs set up their cars to understeer because it's the safer way to go for 99+% of drivers.  Mid or rear engine cars will oversteer, but it takes a trained driver to keep the car from ending up in a ditch.  Check out the number of bashed Porsches on  w www.wreckedexotics.com (http://www.wreckedexotics.com) w  if you doubt me.
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Post by: dieamond on November 10, 2005, 07:02
i just bought hankook K107

front 195/40R17

rear 215/35R17

pretty good no ?

430Euros, less than 300£ on 123pneus.com
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Post by: Anonymous on November 10, 2005, 21:55
What size were the wheels?  And, how does it handle?  Do you drive just on the street? or do you imagine you're always on a track?
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Post by: kanujunkie on November 10, 2005, 22:05
Quote from: "dieamond"i just bought hankook K107

arn't the Hankooks a background company for Toyo's???

a mate told me this but never heard it confirmed  s:? :? s:?
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Post by: dieamond on November 10, 2005, 22:20
Toyo -> japanese

Hankook -> korean
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Post by: kanujunkie on November 10, 2005, 22:23
doesn't mean Toyo's dont own Hankooks though
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Post by: dieamond on November 10, 2005, 22:28
yeah, but I don't think so
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Post by: kanujunkie on November 10, 2005, 22:33
cool cheers Dieamond
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Post by: dieamond on November 10, 2005, 22:37
they seem in competition here in France in term of sponsorship, that's why  s;-) ;-) s;-)
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Post by: Anonymous on November 23, 2005, 17:37
Hi Found a great thread on Spiderchat   m http://www.spyderchat.com/phpBB/viewtop ... e+pressure (http://www.spyderchat.com/phpBB/viewtopic.php?t=25795&highlight=tyre+pressure) m .

tried standard set first, only ok. Then tried Carvers. Brillant much better. not at all what I expected but works.

Thanks for the Help folks
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Post by: Anonymous on December 21, 2005, 17:45
Just as a pointer now a good 2000 miles since I tried Carvers Set up. Still good. although I had one scary moment of Snap Oversteer last thur coming off a roundabout. easily controlled on a good road but like everything in life, a bit scary the first time.  not sure I'd recommend somebody to try 205's all round though. I like it but I think in terms of performance you'd probabley be better staying stock and lowering your ride height. However in terms of appearence the 17's do look fantastic.

Just one more problem. MUD even with the mud flaps the wider wheel trows the stuff everywhere. I only got it washed this morning and already theres mud all over the lower door. Not helped by the car being yellow either!
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Post by: kanujunkie on December 21, 2005, 18:00
you are talking about a thread started by the guru, sorry the God of Mr2's

the one
the only

Mefarri!!

jinxed from the start  s:? :? s:?
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Post by: Anonymous on December 21, 2005, 18:03
Obviously a story here I haven't heard yet. Anyone care to inform me?
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Post by: Anonymous on December 21, 2005, 18:08
Go to SC and read all of Mefarri's posts. You'll see that 99.9% of them are questions, and he has no idea what he's talking about.

If the MR2 community had a clown, then Mefarri would be wearing the biggest shoes, trousers and red nose you could find.
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Post by: Anonymous on December 21, 2005, 18:19
Bit Harsh, arn't everybodys posts questions?
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Post by: markiii on December 21, 2005, 18:20
there are questions and there are questions, you really need to read them to understand.
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Post by: Anonymous on December 22, 2005, 12:42
Checked out posts, point conceeded