Why do prodrive recomend ?
#1
Why do prodrive recomend that 18" wheels should be used on the sti 8 ppp ?
Are there any performance gains to be had by adding the larger rims ?
Has anyone done this modification ? any pros ? any cons ?
cheers
chris.
Are there any performance gains to be had by adding the larger rims ?
Has anyone done this modification ? any pros ? any cons ?
cheers
chris.
#5
18's are likely to weigh more than 17's. Tyre wall will be considerably shorter, which is not necessarily a good thing on british roads, despite how well it will seem to go on smooth tarmack race track. I suspect it is, at least moderately, a profit based recommendation.
#6
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I don`t care what they say about the 18" wheels, I think the standard wheels are tops! Also they must be the easiest wheels ever to clean, unlike most of the 18" options with corner bits that`ll hold brake dust and grime.
I imagine by putting the spring kit on, it will give sharper handling than any 18" wheel upgrade
I imagine by putting the spring kit on, it will give sharper handling than any 18" wheel upgrade
#7
re: unsprung weight. You obviously need to take in to account the tyre as well as the wheel, so if you are able to make a wheel larger but keep the weight the same, the unprung weight may be reduced.
The reason for the recommendation will probably be purely that the set-up has been developed for that specific wheel, etc. The benefits of a shorter tyre wall include things like sharper / quicker reaction, less deformation of the contact patch with slip angle, etc. There are negatives too, but the whole set-up has probably been designed to make the most benefit of that wheel.
Cheers
Simon
The reason for the recommendation will probably be purely that the set-up has been developed for that specific wheel, etc. The benefits of a shorter tyre wall include things like sharper / quicker reaction, less deformation of the contact patch with slip angle, etc. There are negatives too, but the whole set-up has probably been designed to make the most benefit of that wheel.
Cheers
Simon
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#9
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Had 17" Oz wheels on mine.
Moved on to 18" prodrive and i take corners much better
And i can still get 5 people in the car with no rubs
Moved on to 18" prodrive and i take corners much better
And i can still get 5 people in the car with no rubs
#11
Hi Simon,
"re: unsprung weight. You obviously need to take in to account the tyre as well as the wheel, so if you are able to make a wheel larger but keep the weight the same, the unprung weight may be reduced."
I was kind of taking this into account. IIRC, lower profile tyres with tiny short sidewalls tend to need much more material in the sidewalls in order to form a useful tyre shape, hence bumping weight up. Also, in general, larger wheels seem to like to be wider too, which adds on the weight again. And this extra mass is added closer to the outside of the wheel, thus making a larger impact in dynamic mass (if thats a relevant term). IYSWIM
"re: unsprung weight. You obviously need to take in to account the tyre as well as the wheel, so if you are able to make a wheel larger but keep the weight the same, the unprung weight may be reduced."
I was kind of taking this into account. IIRC, lower profile tyres with tiny short sidewalls tend to need much more material in the sidewalls in order to form a useful tyre shape, hence bumping weight up. Also, in general, larger wheels seem to like to be wider too, which adds on the weight again. And this extra mass is added closer to the outside of the wheel, thus making a larger impact in dynamic mass (if thats a relevant term). IYSWIM
#12
Hi Moray
A taller sidewall tends to need more material due to it needing to add stiffness (for obvious reasons).
It's a common consideration in development to consider the addition of mass in larger wheel compared to the reduction in mass due to lower profile tyre.
The "dynamic mass" thing is not a consideration in pure un-sprung weight discussion.
My personal gut feeling is that 17 is a large as I would want to go on a scooby, but I didn't develop the set-up so I can't recomend either way.
Cheers
Simon
A taller sidewall tends to need more material due to it needing to add stiffness (for obvious reasons).
It's a common consideration in development to consider the addition of mass in larger wheel compared to the reduction in mass due to lower profile tyre.
The "dynamic mass" thing is not a consideration in pure un-sprung weight discussion.
My personal gut feeling is that 17 is a large as I would want to go on a scooby, but I didn't develop the set-up so I can't recomend either way.
Cheers
Simon
#14
I have the 18" on my STi PPP but never drove it with the 17's however I don't notice much in the way of understeer apart from in the wet. Understeer seems to be talked about with STi when running on 17's hence I assume from this that the 18's go someway to remedy this problem
Or maybe I'm braking too early
Or maybe I'm braking too early
#15
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I have the Prodrive FF7s on my STi 7 and I *think* that the ride actually improved slightly (placebo anybody? ). IIRC, the OE STi wheels are rather heavy and that the FF7s are a couple of kilos lighter per corner, which would probably explain the ride thing - I have no idea if the 18" tyres are heavier or lighter than the 17s however, but I would imagine if the wheel weight is correct, it is a net gain.
I like them and would recommend them to any STi owner considering them.....
Matt
I like them and would recommend them to any STi owner considering them.....
Matt
#16
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Moray & Mutant
I weighed the std. STi7/8 17" wheel/tyre and the Prodrive 18" FF7/Toyo 225/40 combo and the bigger wheel was knocking 3kg lighter! My sons 18" OZ 10 spoke/P-zero Nero was a little heavier but still noticably lighter than the standard set-up.
The PPP version that Clarkson raved about (and the "Stig" flogged around the track) on Top Gear a few weeks back had the standard set-up!
JohnD
I weighed the std. STi7/8 17" wheel/tyre and the Prodrive 18" FF7/Toyo 225/40 combo and the bigger wheel was knocking 3kg lighter! My sons 18" OZ 10 spoke/P-zero Nero was a little heavier but still noticably lighter than the standard set-up.
The PPP version that Clarkson raved about (and the "Stig" flogged around the track) on Top Gear a few weeks back had the standard set-up!
JohnD
#18
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Hi Tony
Get off this BBS and do some work! I don't go back until the 1st These long hols make it really hard when you have to go back, and you know the little b******s I "teach" (sympathy please - anyone?)
Car will be washed tomorrow. If I clean it too soon it might get some dust on it!
JohnD
PS they're both PPP'd
Get off this BBS and do some work! I don't go back until the 1st These long hols make it really hard when you have to go back, and you know the little b******s I "teach" (sympathy please - anyone?)
Car will be washed tomorrow. If I clean it too soon it might get some dust on it!
JohnD
PS they're both PPP'd
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Bear in mind i'm on a classic but:
better turn in and road holding with my 18's, over the 17's.
But the cons are it's a little bit bumpier (but not as bad as I'd imagined) and they're EXPENSIVE!
So I guess Prodrive recommend them cos they get more money off ya and the car handles better.
better turn in and road holding with my 18's, over the 17's.
But the cons are it's a little bit bumpier (but not as bad as I'd imagined) and they're EXPENSIVE!
So I guess Prodrive recommend them cos they get more money off ya and the car handles better.
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