rodgling
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| posted on 18/9/12 at 07:08 PM |
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changed my wheels, now car feels very different
In my search for lighter wheels, I ended up getting some adaptors to allow me to fit Japanese wheels, which means that my new wheels start off 25 mm
further out, and being of a different offset, move the centre of the tyre out by a total of about 35 mm each side! Also the car is of course
0.5" lower (16" down to 15" wheel). The wheels look awesome though and they weigh 4.8 kg per rim so they must be good :-)
Additionally, they came with 15" 205 AD08 tyres on the front (I had 16" 225 T1Rs on the front before, which was rather over-tyred). I have
20 psi all round (700 kg car).
This means I now have a lot of positive scrub radius, which I had expected to give more steering feel. However, the steering now feels very very light
(before it was very very heavy) and a little lacking in feedback.
I would like more feedback / feel, don't mind if it makes the steering a little heavier again. What can I try?
[Edited on 18/9/12 by rodgling]
[Edited on 18/9/12 by rodgling]
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Coopz
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| posted on 18/9/12 at 07:19 PM |
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We need pictures 
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snapper
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| posted on 18/9/12 at 07:19 PM |
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Toe, camber, tyre pressures
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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mikeb
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| posted on 18/9/12 at 07:24 PM |
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The narrower width will make the steering lighter, the inrease in scrub should give u less feel, zero scrub is the aim.
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motorcycle_mayhem
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| posted on 18/9/12 at 07:32 PM |
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I assume you really meant you had 16" 225's, I may be wrong, but everything else you say seems to fit a reduction of both diameter and
profile. This is a good thing.
A 16" 225 seems a great Land Rover tyre.... I'll assume that you haven't built a 4 by 4, but at 700Kg I suspect a trace of Pinto
mentallity.
OK, your scrub is greater, but the tyres narrower, you've balanced things perhaps. As the previous guy says, check camber, toe and castor. A bit
of rake might help whatever, so get out the scales too. Also, when it drives, assess understeer/oversteer and think again.
All my moped powered things were happier on still narrower tyres than you have at the front (and 13" diameter). Then again, most were on slicks.
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rodgling
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| posted on 18/9/12 at 07:43 PM |
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Yes, I've gone from 16" to 15". I would expect the narrower tyre to reduce steering effort a bit, but not to the extent that it
has.
Everything I've read suggests that big scrub radius will be good for steering feel, with the main downside being poor stability under braking
(especially if you lock a wheel).
The car is now a bit too low so I can try adding rake - but this won't have changed. Apparently increasing scrub radius increases dynamic toe
out so perhaps I can toe it in a bit to get back to where it was?
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rodgling
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| posted on 18/9/12 at 07:45 PM |
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quote:
Originally posted by Coopz
We need pictures
No photos on the car yet, but it's these: Wedsport 15' forged very lightweight alloys / yokohama tyres - MINT - 5x114 pcd |
eBay - they look great on a white car.
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britishtrident
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| posted on 18/9/12 at 08:24 PM |
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Steering feel largely comes from sidewall deflection which is largely down to side wall stiffness, load and inflation pressure.
Even at a car weight of 700kg your front tyres are carrying a lot less load than they were designed for 20psi in the front tyres is high try
14psi
This graph is for a 195/50 R15 tyre
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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rodgling
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| posted on 18/9/12 at 08:31 PM |
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Yeah, I think that will be the first thing to try. Not least because it's the easiest thing :-)
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daniel mason
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| posted on 18/9/12 at 09:40 PM |
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am i correct in thinking youve added +70mm track width?
cant see that doing the handling much good myself but may be wrong!
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rodgling
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| posted on 18/9/12 at 10:04 PM |
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quote:
Originally posted by daniel mason
am i correct in thinking youve added +70mm track width?
cant see that doing the handling much good myself but may be wrong!
Yes, about 70 mm (I guess about a 5% increase). If my understanding is correct this should reduce lateral weight transfer and roll (good), lower the
effective spring rate (not a big deal), and make it less stable at high speed due to shorter wheel base ratio (bad). I think overall it probably will
be fine, what problems do you foresee?
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rodgling
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| posted on 20/9/12 at 10:34 AM |
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Tyre pressures dropped to 16 psi all round, result is a huge improvement. Vague floaty feeling is gone, replaced by quite good feel in the steering.
Might try going a bit lower and seeing how that feels.
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rodgling
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| posted on 20/9/12 at 01:00 PM |
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And here's what they look like on the car. I really like them:
Will look into getting some uprights made which take the right hubs for the wheels without needing an adaptor, but for now this arrangement seems to
be doing the job.
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rodgling
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| posted on 23/9/12 at 10:04 AM |
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quote:
Originally posted by rodgling
quote:
Originally posted by daniel mason
am i correct in thinking youve added +70mm track width?
cant see that doing the handling much good myself but may be wrong!
Yes, about 70 mm (I guess about a 5% increase). If my understanding is correct this should reduce lateral weight transfer and roll (good), lower the
effective spring rate (not a big deal), and make it less stable at high speed due to shorter wheel base ratio (bad). I think overall it probably will
be fine, what problems do you foresee?
Did a sprint on the new setup yesterday. Happy to report that increasing track by 70 mm and scrub radius by 35 mm has not hurt the handling - car
performed very well on the new setup and was nice and progressive in terms of oversteer. No understeer, ever, which seems a bit imbalanced but
it's always done that - it's not a new problem. Managed 1.1 g laterally / 0.85 under braking on road tyres which seems quite good?
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