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Phantom_Mark 
Senior Member II
Joined: 21-September-2004
Location: Lincoln UK
Status: Offline
Points: 194
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 Topic: Wrong tyre sizes ?
Posted: 05-December-2004 at 08:53 |
I Just managed to pick up and fit a set of 17inch wheels for my car.
Front tyres are Kumho 245.40.17's, Rears are 245.45.17's.
Now my gut feeling is that the fronts should be 225's rather than the 245's currently fitted ?
Car has massively more grip in the wet than my old M+S 195/15's  , but thats completely what I was looking for.
Can anyone please tell what pressures I should be runnin on these tyres ? I guessed on 32 front 34 rear but the front end tram lines terribly on white lines and bad surfaces especialy under braking.
Also when I removed my old wheels I noted I had some spacers fitted ? I have not put them on with these new wheels as I guessed they were only fitted to boost the track width with the smaller wheels that were originaly on the car.
Also wondering if my speedo will be accurate or not now ? if not how can I sort this out - either that or can someone approximate how far out the speedo will be.
Thanks very much :)
Mark.
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<<<<< The only way is up >>>>
( unless your in a 5 series, then sideways is cool too )
91' 525 24v Sport, Stainless Race Manifolds, PowerFlo Stainless + Decat, Big Bore Throttle Body, Viper 2 Chip + 17's, std BMW Air Filter :D
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e34m5
Really Senior Member II
Joined: 26-June-2003
Location: Near Rugby, Warwickshire
Status: Offline
Points: 1344
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Posted: 05-December-2004 at 10:17 |
O.E. fit tyres (as fitted to the E34 M5 and some 540's) would be :
235 40 17 = an overall tyre diameter of 25.33"
a 245 40 17 = 24.72" which is within the recommended +-2.5% so they should be fine
the rear 245 45 17 = 25.68" which is also within the +-2.5%
Your speedo will be reading 1.4% over what it should which should compensate for the fact that they always read a couple of MPH under what you are actually doing anyway
The tyres pressures sound ok but you could do with increasing them a little.
If the wheels are the correct offset of around ET20 you won't need spacers.
Miles
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Phantom_Mark
Senior Member II
Joined: 21-September-2004
Location: Lincoln UK
Status: Offline
Points: 194
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Posted: 05-December-2004 at 15:11 |
Dont you think the 245 fronts are a little over the top tho Miles ?
Thanks for the other info..sugeested tyre pressures in your opinion ?
Would the fronts being too wide be causing the horrible tram-lining feeling I have - or just pressures you think ?
Cheers
Mark.
|
<<<<< The only way is up >>>>
( unless your in a 5 series, then sideways is cool too )
91' 525 24v Sport, Stainless Race Manifolds, PowerFlo Stainless + Decat, Big Bore Throttle Body, Viper 2 Chip + 17's, std BMW Air Filter :D
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e34m5
Really Senior Member II
Joined: 26-June-2003
Location: Near Rugby, Warwickshire
Status: Offline
Points: 1344
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Posted: 05-December-2004 at 15:32 |
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I am running 245 fronts with my 19" wheels and don't experience any noticeable tram-lining.....Try increasing the front tyre pressures by a couple of PSI to see if the problem is reduced...You should run the backs about 2 psi higher than the fronts.
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JamesE30
Groupie
Joined: 03-December-2002
Location: United Kingdom
Status: Offline
Points: 98
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Posted: 06-December-2004 at 05:47 |
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Mark,
I run 255/40 R17 on the back of my 5 and 235/45 R17's on the front and do experience a bit of tramlining.
I have now bought two 225/45's for the front and plan to fit them when the 235's wear out, to try and alleviate this. To be honest I attribute the tramlining to the slight wear in the steering which is accentuated by the 235's I am now running rather than the car just having wider tyres.
Interestingly in Total BMW last month someone had written in with a similar query and the advice given was to down size to 225's.
Good Luck,
James
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Phantom_Mark
Senior Member II
Joined: 21-September-2004
Location: Lincoln UK
Status: Offline
Points: 194
|
Posted: 06-December-2004 at 07:02 |
Thanks very much
|
<<<<< The only way is up >>>>
( unless your in a 5 series, then sideways is cool too )
91' 525 24v Sport, Stainless Race Manifolds, PowerFlo Stainless + Decat, Big Bore Throttle Body, Viper 2 Chip + 17's, std BMW Air Filter :D
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e34m5
Really Senior Member II
Joined: 26-June-2003
Location: Near Rugby, Warwickshire
Status: Offline
Points: 1344
|
Posted: 06-December-2004 at 08:13 |
If the wheels are 8" wide you will find that a 225 tyre will not provide the rim protection that a 235 tyre would, the rim will stick out further than the tyre 
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Phantom_Mark
Senior Member II
Joined: 21-September-2004
Location: Lincoln UK
Status: Offline
Points: 194
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Posted: 14-December-2004 at 08:37 |
Im confused now.....
Had bad traction on the old 195's, regularly spinnin up the rears when power shifting from 2nd to 3rd in the wet.
Now I got these 245's on the back end I wrong assumed those kinda of problems would be gone.
Last night I was on little more than a cold slightly damp road, typical Lincolnshire country lane with a little camber. I was powering hard nearly to red line in 2nd past another car overtaking shifting hard into 3rd as I went by, to my complete surprise it spun up causing a brief powerslide as I went by - not a problem but just wasnt expecting it, im sure the guy I was overtaking didnt appreciate it either 
Anyone else get these kind of traction problems even with massive rear tyres on the car ? car in general grips massively better with new wheels and tyres on it compared with the powerslide city std 15's and 195 M+S tyres 
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<<<<< The only way is up >>>>
( unless your in a 5 series, then sideways is cool too )
91' 525 24v Sport, Stainless Race Manifolds, PowerFlo Stainless + Decat, Big Bore Throttle Body, Viper 2 Chip + 17's, std BMW Air Filter :D
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e34m5
Really Senior Member II
Joined: 26-June-2003
Location: Near Rugby, Warwickshire
Status: Offline
Points: 1344
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Posted: 14-December-2004 at 09:06 |
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If the tyres are brand new it will take a couple of hundred miles for them to reach full grip....
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Phantom_Mark
Senior Member II
Joined: 21-September-2004
Location: Lincoln UK
Status: Offline
Points: 194
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Posted: 14-December-2004 at 09:29 |
No they are not new, about 3 - 4mm on the rears 2 - 2.5mm on the fronts
Slight OT: I got one of those K+N Panel filters Miles, did I read somewhere you have a drilled Airbox ? or was that andrew ? would love to add some induction road but scared of introducing heat soak - hence the choice of the panel filter in the first place, if its not advisable to drill the airbox would it be worth investing in a custom air scoody from below front ( open the bumper slats maybe ? ) ?
Cheers
Mark.
|
<<<<< The only way is up >>>>
( unless your in a 5 series, then sideways is cool too )
91' 525 24v Sport, Stainless Race Manifolds, PowerFlo Stainless + Decat, Big Bore Throttle Body, Viper 2 Chip + 17's, std BMW Air Filter :D
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e34m5
Really Senior Member II
Joined: 26-June-2003
Location: Near Rugby, Warwickshire
Status: Offline
Points: 1344
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Posted: 14-December-2004 at 09:33 |
 Phantom_Mark wrote:
No they are not new, about 3 - 4mm on the rears 2 - 2.5mm on the fronts
Slight OT: I got one of those K+N Panel filters Miles, did I read somewhere you have a drilled Airbox ? or was that andrew ? would love to add some induction road but scared of introducing heat soak - hence the choice of the panel filter in the first place, if its not advisable to drill the airbox would it be worth investing in a custom air scoody from below front ( open the bumper slats maybe ? ) ?
Cheers
Mark. |
Can't say i have noticed the back end of the car misbehaving unless i really push it around roundabouts....No i haven't drilled my airbox and haven't seen favourable reviews of the k+n replacement panel filters...The original BMW ones filter the air better as they have a much greater surface area...The airbox is already fed cold air from behind the headlight.
Miles
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Phantom_Mark
Senior Member II
Joined: 21-September-2004
Location: Lincoln UK
Status: Offline
Points: 194
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Posted: 14-December-2004 at 09:37 |
Oh well maybe it will work better when I combine it with the chip and exhuast after chrimbo 
Damned idle control valve to fix still - and thats really pi**** me off to be honest
Thanks Miles....
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<<<<< The only way is up >>>>
( unless your in a 5 series, then sideways is cool too )
91' 525 24v Sport, Stainless Race Manifolds, PowerFlo Stainless + Decat, Big Bore Throttle Body, Viper 2 Chip + 17's, std BMW Air Filter :D
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e34m5
Really Senior Member II
Joined: 26-June-2003
Location: Near Rugby, Warwickshire
Status: Offline
Points: 1344
|
Posted: 14-December-2004 at 09:43 |
Phantom_Mark wrote:
Oh well maybe it will work better when I combine it with the chip and exhuast after chrimbo
Damned idle control valve to fix still - and thats really pi**** me off to be honest
Thanks Miles.... |
The chip will definitely make a difference
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Wrong tyre sizes ?
