Rear Trailing Arms - Poly bush or rubber bush ?

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MikeyBikey
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Rear Trailing Arms - Poly bush or rubber bush ?

Post by MikeyBikey » Mon Jul 16, 2018 10:14 pm

I'm pretty certain the rhs rear, upper trailing arm, forward bush is failing. Its wallowing and when I pull away promptly, eg sprinting, she squats on that side.

She's going in the garage, on a lift this Friday to check but if it is , do i poly bush them or replace with the rubber (metallistic ?) type ones. Ive heard polybushing the rear is a no go, too harsh but that might be just hearsay. ?

cheers


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Rear Trailing Arms - Poly bush or rubber bush ?

Post by Coupe Racing » Tue Jul 17, 2018 4:43 pm

My SE5a always squatted to one side under hard acceleration.
The bushes hold the axle in a lateral location IE in the X and Y plane
I would look to see if I could stop the torque reaction through the chassis if I were you


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Rear Trailing Arms - Poly bush or rubber bush ?

Post by efi_sprintgte » Tue Jul 17, 2018 4:50 pm

Coupe Racing wrote:
Tue Jul 17, 2018 4:43 pm
My SE5a always squatted to one side under hard acceleration.
The bushes hold the axle in a lateral location IE in the X and Y plane
I would look to see if I could stop the torque reaction through the chassis if I were you

Cars that don’t have their pick ups relocated do that.


I run polys on my track cars and trying rubbers on my roadie.

That being said dads tow car has polys in the rear and so did my 5a when it was a road car, both were fine.


JC

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Rear Trailing Arms - Poly bush or rubber bush ?

Post by scimjim » Tue Jul 17, 2018 8:10 pm

I’ve been in a road car with poly and it made a hell of a noise - however, that was many years ago and poly has improved a lot since then.


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Rear Trailing Arms - Poly bush or rubber bush ?

Post by GavinR » Thu Jul 19, 2018 10:25 pm

Mine's polybushed all round, but I'm not worried about noise, I just wanted something that would stand up to the abuse it was going to get!


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Rear Trailing Arms - Poly bush or rubber bush ?

Post by MikeyBikey » Thu Jul 19, 2018 10:47 pm

Thurs night : So I removed both rear shocks, then removed springs from shocks. All appears ok. So re assembled but refitted on opposite sides. Tomorrow will try some launches and if the squat has moved sides, I know it’s the shock. If not it’s the chassis somehow.

Edit : Friday morning. Been up with the larks. Beautiful morning - again. Really this is the best spell of decent weather we have had for years. Anyways scared the birds, woke the neighbours etc etc the car is still squatting on the right. If you briefly turn your head around when you launch and watch the rear of the car its quite pronounced.

So its not shocks....

Steve you mentioned torque ??


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Rear Trailing Arms - Poly bush or rubber bush ?

Post by MikeyBikey » Fri Jul 20, 2018 8:02 am

PS the shocks didn't extend unless the spring is present. IE if you push them in they don't push themselves out ? is that normal


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Rear Trailing Arms - Poly bush or rubber bush ?

Post by Martin Rowe » Fri Jul 20, 2018 9:09 am

Engine Torque will make one side squat more than the other.



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Rear Trailing Arms - Poly bush or rubber bush ?

Post by Coupe Racing » Fri Jul 20, 2018 9:28 am

MikeyBikey wrote:
Thu Jul 19, 2018 10:47 pm


Steve you mentioned torque ??
Yes I did
Your axle needs locating better, maybe a different setting or as James says , look at the way the axle is located and how the torque from the engine is transmitted through the drive train


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Rear Trailing Arms - Poly bush or rubber bush ?

Post by b.c.flat hat » Fri Jul 20, 2018 9:31 am

MikeyBikey wrote:
Fri Jul 20, 2018 8:02 am
PS the shocks didn't extend unless the spring is present. IE if you push them in they don't push themselves out ? is that normal
Some do cos they're pressurised wi' nitrogen or some such, others don't. Guess which costs more😡



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Rear Trailing Arms - Poly bush or rubber bush ?

Post by derekoss » Fri Jul 20, 2018 10:10 am

Every action has an opposite reaction. The powertrain is turning one way. In this case firmly attached to body/chassis. The axle is flexibly attached to said body/chassis.
When you pour the power on it is initially easier for the body/chassis to rotate the opposite way in relation to the axle rather than transmit torque through the axle. Eventually it depresses the spring to the limit required and everything is balanced. Albeit at an angle.
A rigid setup would prevent that but wouldn't be comfortable. Introduce springs and shocks. How strong these are depends on the application.
I guess the ideal would be air or hydraulic springs automatically biased as the power comes on. The torque has to go somewhere until the axle catches up. It goes into the spring then subsequently released.
Over simplification I know but might help.

Derek



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Rear Trailing Arms - Poly bush or rubber bush ?

Post by MikeyBikey » Fri Jul 20, 2018 4:36 pm

Cheers. The garage say the trailing arm bushes are fine. So I’ve booked her into the local independent diff / gearbox centre. It’s the only one in Cornwall. Tbh I’d prefer someone like Richard have a look but he’s about 5 light years from where I live...


Is we sideways yet...

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