Pete McCluskey.
Lifetime Supporter
:lol: Jim, love your sense of humour. Nice web site also.
What causes heavy steering at racing speeds
- Thread starter Russ Noble
- Start date
:lol: Jim, love your sense of humour. Nice web site also.
Paul,
If you look carefully at the photos posted by Ross N you will see he has the rotation wrong, the directional arrows are visible. It would appear that at some time he has swapped the wheels over from L to R
If you look carefully at the photos posted by Ross N you will see he has the rotation wrong, the directional arrows are visible. It would appear that at some time he has swapped the wheels over from L to R
I think you will find the tyres are correctly fitted. Assuming Ross has the pics in sequence -top 3 = LF, Bottom 3 = RF. The arrow that would indicate they are INCORRECT has DRIVE beside it, I think those tyres have two sets of arrows from memory and the other arrow would indicate correct fitment for a front non-driven wheel!
Jac Mac
Sorry Ross - I did mean to say Cortina! Glad your bearings are in good shape.
I'm looking forward to your Sandown results and more video.
Ross Nicol
GT40s Supporter
Gee it's amazing what you guys are picking up from my photos. I thought you would be bored with them black doughnuts. Interesting this drive arrow thing. There is only one arrow with the word Drive next to it. The Dunlop tyre man has told me that on the front it's not really critical which way the drive arrows face but he did say a lot of users point the arrows backwards as braking loads are that way. These tyres are Radials by the way which could account for differing pressures.
Ross
Ross
Ross Nicol
GT40s Supporter
Jac Mac yes I checked the pics for order the top 3 are the LH and the lower 3 the RH as you thought.
Ross
Ross
Thats good Ross, I was having a bit of trouble making sure on that from over here, just as well old age has left me good vision from this distance, although the snowstorm's going thru here at the moment are not helping, if I was over in Aussie I would be using my braille skills!!!
Jac Mac
It Is off to the optometrist for trevor !! I could not read the word drive until it was pointed out.
I'm sure someone said no question is too dumb so here goes, How do I start a thread for my build ?
Ross
Have you tried Michellins ? I have found the level of tech support extreemly valuable and with their contract with Carrera Cup you can rely on getting "fresh" tyres as opposed to tyres that may have been on the rack for 6 months.
Iain
Ross
Have you tried Michellins ? I have found the level of tech support extreemly valuable and with their contract with Carrera Cup you can rely on getting "fresh" tyres as opposed to tyres that may have been on the rack for 6 months.
Iain
Iain,
Click on 'The Builders Forum' in this 'GT40 Technical Forums' Section. Then click on the ' New Thread ' Box at top LH of the page.
Jac Mac
Iain
When you make your thread you just keep adding to the same one over time.
Dont make a second or Ron will get angry.
Jim
When you make your thread you just keep adding to the same one over time.
Dont make a second or Ron will get angry.
Jim
Ross Nicol
GT40s Supporter
Iain
What's this trying to get me to use tyres as used by the dreaded P........e
brigade. No way fresh or not. I'm sure they must cost twice the price of my Dunlops. However you never know what Ross might do in the future to lower his lap times. Do they run 17" wheels in Carrera Cup? I must say I do get good service from the Dunlop guys they never charge for tyre changes or rotation.
Ross
What's this trying to get me to use tyres as used by the dreaded P........e
brigade. No way fresh or not. I'm sure they must cost twice the price of my Dunlops. However you never know what Ross might do in the future to lower his lap times. Do they run 17" wheels in Carrera Cup? I must say I do get good service from the Dunlop guys they never charge for tyre changes or rotation.
Ross
Plus if you use the same tyre and beat them then your 40 is obviously a superior car and you are a class act as a driver, whereas if you beat them on those dunlops they-( those P people ) will twist it to make it look like you have an unfair advantage!!
Jac Mac
Ross Nicol
GT40s Supporter
Yep when I thrashed them in the wet one of them stated 'oh yes but your driving a race car ' That's why I hate them, mind you I think the VW tag hurts them a lot. 18" no good for me I'm on 17" Iain. What's with the 'Straight 8' tag Iain neither Cobra or GT40 are long enough for 8 cylinders in a single row. Now where's Russ I've knicked his thread and he's not around at the moment, must be dreaming about 930 transaxles, oh well.
Ross
Ross
Chris Duncan
Supporter
In regards to Trevor's comment about zero scrub I will say I've never tuned suspension for racing. The zero scrub idea was from "Chassis Engineering" by Herb Adams. That said I will be dialing for a track day shortly and the G-meter tuning tool is on it's way so their will be G numbers to confirm.
So maybe I got accidentally lucky when not being able to get to zero scrub, because with 20mm it feels right.
From reading this thread it's apparent that both Scrub and Caster contribute to Tracking. So total tracking is the sum of these two settings. What if you reduced the one that's easier to adjust to reduce the total? That would be Caster of course, and assuming you have some range left in the adjustment.
It looks like Ross's caster settings are standard for a car that has standard scrub which he does not. The goal is to reduce heavy tracking, does is matter how you skin the cat?
Keep in mind this is armchair shadetree engineering, no guarantees expressed or implied
Just guessing here but you'd think the scrub load would be almost zero in pits and increase with road speed while the caster load would be more of a steady state, not changing as much with road speed? Thoughts anyone?
So maybe I got accidentally lucky when not being able to get to zero scrub, because with 20mm it feels right.
From reading this thread it's apparent that both Scrub and Caster contribute to Tracking. So total tracking is the sum of these two settings. What if you reduced the one that's easier to adjust to reduce the total? That would be Caster of course, and assuming you have some range left in the adjustment.
It looks like Ross's caster settings are standard for a car that has standard scrub which he does not. The goal is to reduce heavy tracking, does is matter how you skin the cat?
Keep in mind this is armchair shadetree engineering, no guarantees expressed or implied
Just guessing here but you'd think the scrub load would be almost zero in pits and increase with road speed while the caster load would be more of a steady state, not changing as much with road speed? Thoughts anyone?
Ross Nicol
GT40s Supporter
I suspect you are right Kalun. I just wish there was an easier way to reduce my scrub radius to prove the theory. There are variables involved though wheel/tyre width for one. I will keep working to resolve it though.
Ross
Ross
Kalun
I agree
I have used a lot of the theory from the Herb Adams book.
I have read numerous books in the last few months and it seemed to keep coming back to the same thing get the upright inside the wheel to reduce scrub radius select a suitable wheel offset and make the lower arm as long as you can.
I spent hours on the cad projecting IC and RC with control arm angles ect and it improves these areas also.
Jim
I agree
I have used a lot of the theory from the Herb Adams book.
I have read numerous books in the last few months and it seemed to keep coming back to the same thing get the upright inside the wheel to reduce scrub radius select a suitable wheel offset and make the lower arm as long as you can.
I spent hours on the cad projecting IC and RC with control arm angles ect and it improves these areas also.
Jim
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Ross Nicol
GT40s Supporter
I spoke to my wheel manufacturer this morning and the smallest practical outer rim he can make is 2". This is good because if I use a 2" outer and a 7" inner I will have the identical rim width I've got now but the wheel centre will be 2" further out.This with longer arms will bring my scrub radius/steering offset down to around 70mm. Another benefit is the 7" inner rim allows for larger brake rotors (if I ever need them). Further benefit is the spare rims left over from this change will be useable on the rear (I planned that! well not really). I will be left with 3 - 5" inner rims I won't be able to use but thems the breaks. I'm still piecing the project together but this is a good start. More to come.
Ross
Ross
