suspension set ups and corner weighting
Discussion
Can anyone please provide me the recommended geometry set ups for a Caterham HPC on 13 inch minilites-for road use
I'm ummhing and arrhing about getting a proper 4 wheel check done although I have to say it feels just fine as it is just now- so maybe its a case if it aint broke ....
I'm assuming its not worth doing corner weighting just for road use -does it radically change the handling of the car even for road use ? For what its worth My HPC is on the std Bilsteins .
I'm ummhing and arrhing about getting a proper 4 wheel check done although I have to say it feels just fine as it is just now- so maybe its a case if it aint broke ....
I'm assuming its not worth doing corner weighting just for road use -does it radically change the handling of the car even for road use ? For what its worth My HPC is on the std Bilsteins .
I'd be surprised if the Geo was far out, knowing history of car but might be worth checking. As a rough guide, measure height of front, from lower chassis rail under rear leg of lower wishbone and this should be about 130 mm. If it's much less, sump might suffer. Using this measurement, the rear, measured from underside of chassis rail just forward of leading edge of rear wing, should be about 15 mm greater than the front.
This is a rough guide only and if the car has been flat floored, it is unlikely that each corner will be equal in measurement.
This is a rough guide only and if the car has been flat floored, it is unlikely that each corner will be equal in measurement.
Just out ignorance and curiosity -if I recall the original HPC was on 16 inch rims-so how would this differ in terms of handling characteristics cf the 13 inch rims -I'm just thinking naively that with larger rims is it going grip the road better with more surface area of rubber ? So what was the reason that folk switched to the 13 inch rims -was it for better handling ,lower centre of gravity or weight ?
doclip said:
Just out ignorance and curiosity -if I recall the original HPC was on 16 inch rims-so how would this differ in terms of handling characteristics cf the 13 inch rims -I'm just thinking naively that with larger rims is it going grip the road better with more surface area of rubber ? So what was the reason that folk switched to the 13 inch rims -was it for better handling ,lower centre of gravity or weight ?
Theoretically the area in contact with the road is determined by the tyre pressure chosen to support the weight - that's way different pressures are often used from front to rear to adjust the balance. The wheel size is about un-sprung weight. The smaller wheel and tyre, the lower the weight, and the contact with the road improves (they follow the bumps and dips better). It also means that you can run bigger profiles which provide more progressive characteristics at the limits of grip. But running bigger wheels does have a place on the road where their 'feel' and looks are important.Edited by DCL on Tuesday 10th June 07:57
If I remember correctly, the car has Bilsteins fitted? If so, they will not be adjustable for rebound/compression but dont worry about that as they are very good shocks and are well suited to the 7 as they are.
In order to change ride heights, you adjust the platforms that the springs sit on. Winding the two collars up the damper thread will increase ride height and winding them down will lower the car. That car felt OK to me, so I dont think it would be that far out.
In order to change ride heights, you adjust the platforms that the springs sit on. Winding the two collars up the damper thread will increase ride height and winding them down will lower the car. That car felt OK to me, so I dont think it would be that far out.
DCL said:
Theoretically the area in contact with the road is determined by the tyre pressure chosen to support the weight - that's way different pressures are often used from front to rear to adjust the balance. The wheel size is about un-sprung weight. The smaller wheel and tyre, the lower the weight, and the contact with the road improves (they follow the bumps and dips better). It also means that you can run bigger profiles which provide more progressive characteristics at the limits of grip. But running bigger wheels does have a place on the road where their 'feel' and looks are important.
Just to add that wheel/tyre width also effects contact area.Edited by DCL on Tuesday 10th June 07:57
Not sure that is true . . .
It might change the shape of the contact patch (and the way the tyre behaves) but if the weight on the tyre is around 330Lbs (150KG) then 18 PSI will require an area of around 18 square inches to support that weight (330/18 = 18.3 square inches). Now that can be a 4.25 x 4.25 or a 9 x 2 patch, but the area will be determined by the tyre pressure. There might be a structural element to the tyre, but in the scheme of things, that is small.
It might change the shape of the contact patch (and the way the tyre behaves) but if the weight on the tyre is around 330Lbs (150KG) then 18 PSI will require an area of around 18 square inches to support that weight (330/18 = 18.3 square inches). Now that can be a 4.25 x 4.25 or a 9 x 2 patch, but the area will be determined by the tyre pressure. There might be a structural element to the tyre, but in the scheme of things, that is small.
You can get lots of nice sticky rubber for 13's that will outperform any 16 tyres and they are cheaper.
Combine that, with as said, lower unsprung mass and you have the reason for 13's.
They spin up faster, corner better, slow down faster and as also said, hug the road better.
With the right tyre they also tramline less.
With 13's you can run more toe out which improve turn in for the VX no end.
You can also play around with camber on the fronts - there's a ratio of turns of trackrod to top link to be observed, or just reset the tracking...
Getting the right camber for a given tyre is a good thing to do. Radials kike Yoko's like much camber. CR500's can handle less. ACB10s and ACB0s little / none.
13's will fall into pot holes more though - perhaps a consideration with todays state of the roads.
Rake is also an important consideration. Rear higher than the front - the build manual prescribes what is a good starting point.
Driver weight can be compensated for by cornerwieghting. For the road one way to look at it is do the fronts to lock up at the same time? Of course no piece of tarmac is ever perfectly flat - even less so when turning into a corner, so it's about getting a balance.
I had a setup I was happy with at some circuits but braking into Druid's at Brands the inside wheel would lock up a bit each time - simple solution, dial some more weight onto it for Brands.
Combine that, with as said, lower unsprung mass and you have the reason for 13's.
They spin up faster, corner better, slow down faster and as also said, hug the road better.
With the right tyre they also tramline less.
With 13's you can run more toe out which improve turn in for the VX no end.
You can also play around with camber on the fronts - there's a ratio of turns of trackrod to top link to be observed, or just reset the tracking...
Getting the right camber for a given tyre is a good thing to do. Radials kike Yoko's like much camber. CR500's can handle less. ACB10s and ACB0s little / none.
13's will fall into pot holes more though - perhaps a consideration with todays state of the roads.
Rake is also an important consideration. Rear higher than the front - the build manual prescribes what is a good starting point.
Driver weight can be compensated for by cornerwieghting. For the road one way to look at it is do the fronts to lock up at the same time? Of course no piece of tarmac is ever perfectly flat - even less so when turning into a corner, so it's about getting a balance.
I had a setup I was happy with at some circuits but braking into Druid's at Brands the inside wheel would lock up a bit each time - simple solution, dial some more weight onto it for Brands.
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