Rolling Resistance
Discussion
I wonder if anyone can help?
When I roll my new R400D in the garage, it starts to roll very freely then there is a drag from somewhere in the transmission line. The free bit is simply the play in the diff and propshaft, I can see that clearly, but I can't figure out where the resistance after that is coming from, the diff, prop or gearbox. It's not the brakes.
It didn't do this when brand new, it has begun after about 5/600 miles. It's only when cold, as soon as it's run for a few minutes the drag disappears and the gearbox changes fine. Once parked and allowed to cool the drag comes back.
Any ideas?
When I roll my new R400D in the garage, it starts to roll very freely then there is a drag from somewhere in the transmission line. The free bit is simply the play in the diff and propshaft, I can see that clearly, but I can't figure out where the resistance after that is coming from, the diff, prop or gearbox. It's not the brakes.
It didn't do this when brand new, it has begun after about 5/600 miles. It's only when cold, as soon as it's run for a few minutes the drag disappears and the gearbox changes fine. Once parked and allowed to cool the drag comes back.
Any ideas?
sjmmarsh said:
Have you got an open diff or LSD? is the wear on the rears even, or has the nearside worn more than the offside? It may be the diff operating if the wheels are rotating at slightly different speeds, but it would be unusual to see this after only 500 miles....
Steve
It's the bmw 3.64 LSD. Over the 600 miles there's no indication of any unusual tyre wear, car tracks straight and roll very easily once warm. Steve
REALIST123 said:
Can the rear track be adjusted and wouldn't that show hot too?
It can be shimmed - there are shimming kit available that adjust toe and camber. My experience is that there tends to be slight toe-in on new cars, but that can change with use, particularly with track driving. Jacking the car on the dion tube can also change it, but seldom enough to be a problem. As for hot and cold. Probably just the tyres relaxing and cooling a bit and I guess you must push it backwards at some stage too
Edited by DCL on Thursday 23 July 21:53
REALIST123 said:
The free bit is simply the play in the diff and propshaft, I can see that clearly
I'm certainly confused about this bit. What play in the diff and the propshaft? How far do you push the car before it's not freely rolling?From my experience I often think Caterhams don't push as easily as they ought for the size and weight anyway.
Bert
BertBert said:
REALIST123 said:
The free bit is simply the play in the diff and propshaft, I can see that clearly
I'm certainly confused about this bit. What play in the diff and the propshaft? How far do you push the car before it's not freely rolling?From my experience I often think Caterhams don't push as easily as they ought for the size and weight anyway.
Bert
To answer your query Bert, as you start to push the car it rolls a couple of inches very easily and then there is a feeling just as if the brakes were binding, which they aren't.
That first free movement is due to the play or backlash in the diff and in the prop/gearbox. If I jack the rear of the car and hold one wheel, the other rotates about 50mm, measured at the shoulder of the tyre, before the prop revolves another 10mm before the play is taken up.
I am now quite sure the drag is coming from the gearbox. If you start the car, in neutral with the clutch disengaged, then release the clutch, the car moves forward a little. To me that indicates viscous drag in the gearbox but I've never seen that except in very low temperatures.
As I've said it all disappears once warm and the gearbox changes fine.
mharris said:
If there was that amount of slack in the drivetrain (to equal a few inches of rolling travel) then I'm pretty sure you would feel that horribly when driving. Are you sure its not a warped disc or something like that?
Brakes are fine.
There is a lot of backlash in the diff, driveshafts and prop. It does feel horrible when driving in that the diff clonks on gearchanges and chatters when you slowly lift off. I posted about that separately and the view seemed to be that TADT. You can adapt to that and avoid most if it.
The drag is definitely in the drive chain and almost definitely in the gearbox. The drag is constant and not there at all when hot.
REALIST123 said:
To answer your query Bert, as you start to push the car it rolls a couple of inches very easily and then there is a feeling just as if the brakes were binding, which they aren't.
That first free movement is due to the play or backlash in the diff and in the prop/gearbox. If I jack the rear of the car and hold one wheel, the other rotates about 50mm, measured at the shoulder of the tyre, before the prop revolves another 10mm before the play is taken up.
I am now quite sure the drag is coming from the gearbox. If you start the car, in neutral with the clutch disengaged, then release the clutch, the car moves forward a little. To me that indicates viscous drag in the gearbox but I've never seen that except in very low temperatures.
As I've said it all disappears once warm and the gearbox changes fine.
Ahh I thought it was several feet! You may be back in the land of TADTS with this as well. But no idea how to check except comparing with someone else with the same setup.That first free movement is due to the play or backlash in the diff and in the prop/gearbox. If I jack the rear of the car and hold one wheel, the other rotates about 50mm, measured at the shoulder of the tyre, before the prop revolves another 10mm before the play is taken up.
I am now quite sure the drag is coming from the gearbox. If you start the car, in neutral with the clutch disengaged, then release the clutch, the car moves forward a little. To me that indicates viscous drag in the gearbox but I've never seen that except in very low temperatures.
As I've said it all disappears once warm and the gearbox changes fine.
Bert
BertBert said:
REALIST123 said:
To answer your query Bert, as you start to push the car it rolls a couple of inches very easily and then there is a feeling just as if the brakes were binding, which they aren't.
That first free movement is due to the play or backlash in the diff and in the prop/gearbox. If I jack the rear of the car and hold one wheel, the other rotates about 50mm, measured at the shoulder of the tyre, before the prop revolves another 10mm before the play is taken up.
I am now quite sure the drag is coming from the gearbox. If you start the car, in neutral with the clutch disengaged, then release the clutch, the car moves forward a little. To me that indicates viscous drag in the gearbox but I've never seen that except in very low temperatures.
As I've said it all disappears once warm and the gearbox changes fine.
Ahh I thought it was several feet! You may be back in the land of TADTS with this as well. But no idea how to check except comparing with someone else with the same setup.That first free movement is due to the play or backlash in the diff and in the prop/gearbox. If I jack the rear of the car and hold one wheel, the other rotates about 50mm, measured at the shoulder of the tyre, before the prop revolves another 10mm before the play is taken up.
I am now quite sure the drag is coming from the gearbox. If you start the car, in neutral with the clutch disengaged, then release the clutch, the car moves forward a little. To me that indicates viscous drag in the gearbox but I've never seen that except in very low temperatures.
As I've said it all disappears once warm and the gearbox changes fine.
Bert
I'm currently trying to arrange for it to go in to Crawley for a check. Might be easier to arrange an audience with the Pope.......
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