transmission warming, wheels off or on?

[eastlmark]

Probably a complete amateur question but... if warming transmission (EG running the driven wheels off the ground) should you keep the wheels on or not or does it matter? I am probably thinking from a safety point of view but not sure what's more dangerous, spinning tyres or spinning bare studs. Obviously car will be safely on stands at the time but if the very worse happened then surely safer without wheels?

[TonykartEVR]

Hi Mark, We jack it up at the front and take wheels off, put it in second or third on low-ish revs

[carl_w]

As you know I'm no expert, but surely it will take longer without the mass of the wheels and tyres connected?

[eastlmark]

carl_w said:

As you know I'm no expert, but surely it will take longer without the mass of the wheels and tyres connected?

You mean warming up? Yes I guess so and I wonder what the effect of having no mass on the end of the drive shafts will have. However, I used the term warming up but really need to run the drive train to check a few things. The reality of a race car is you cannot run it up the road to test work you have done and to turn up at a race and find an issue straight away is an expensive way to find out.

[TonykartEVR]

https://m.youtube.com/watch?v=jrwOsJK6kH8

Cleland must be doing it wrong as well...

[RobM77]

Do check your championship regs, as some specifically disallow this.

[BertBert]

Interesting. What car needs the transmission warmed?
Bert

[eastlmark]

BertBert said:

Interesting. What car needs the transmission warmed?
Bert

Not so much warming, I used the term loosely as explained earlier, more that I need to run the drivetrain to check a few things.... and it will be at my workshop rather than in the paddock.

[andrewcliffe]

Some people run without the wheels, but tighten down the wheel nuts so the brake discs are running true. It helps preserve the clutch.

[tristancliffe]

Having the wheels on can lead to large torque stresses in the driveshafts. Always best to take them off unless you have driveshafts to spare. If you need to clamp the discs then make a little spacer thing held on by wheel nuts.

[Chunkychucky]

BertBert said:

Interesting. What car needs the transmission warmed?
Bert

Older stuff can benefit significantly when it comes to prolonging life over short runs eg. Sprinting/hillclimbing, remember discussing this with Mac Hulbert as he warmed the box on his ERA, which had the wheels at the time

[Greensleeves]

tristancliffe said:

Having the wheels on can lead to large torque stresses in the driveshafts.

Really?

With the weight of the wheels, drive shafts are torque stressed more than the power of the engine going through them?