Trailing arm mods?
Discussion
Got my UJ fixed. The mechanic seriously dissed the trailing arm setup though, and was not surprised these cars eat UJs.
He said the lack of a slip joint in the drive shafts meant that the differential and all the UJs are put under very serious strain especially when cornering hard etc..
Has anyone either tweaked the rear suspension or gone to town on it? If so how, and with what results?
This guy reckons he could make slip jointed shafts for me that would have some give rather than just putting more strain on the suspension, with the result of better handling, far less wear and no axle tramping on hard acceleration from standstill.
He said the lack of a slip joint in the drive shafts meant that the differential and all the UJs are put under very serious strain especially when cornering hard etc..
Has anyone either tweaked the rear suspension or gone to town on it? If so how, and with what results?
This guy reckons he could make slip jointed shafts for me that would have some give rather than just putting more strain on the suspension, with the result of better handling, far less wear and no axle tramping on hard acceleration from standstill.
Yes, driveshafts hold the track, adjusted by the shims between driveshaft and brake disks. Sliding joints in the driveshafts would make for some very interesting handling. New ujs are cheap and easy to fit, Unfortunately the driveshaft is not so easy to remove and refit. Worth the effort to get under there and grease the ujs yourself every 1000 miles / 3 months.
It's cobblers about this 'slip joint'. What the car needed was wishbones, or at least a better way of locating the trailing arm. Triumph had used a similar setup for years , as had Lotus.... Porsche, Skoda and several others. The basic design (and indeed some of the same components) was also used by Jaguar. It was the TVR interpretation of it that wasn't spectacular... though to be fair it wasn't really any worse than anyone else's, just had more power applied!
IMHO wishbones are God.
Ian
IMHO wishbones are God.
Ian
wedg1e said: Triumph had used a similar setup for years
Not quite, Triumphs used a slip joint in the drive shaft with the trailing arms having inner and outer pivot points to set the geometry. These slip joints are fine if they are well lubricated but can stick, then free off again coming out of a bend leading to the infamous "Triumph twitch"
But they are much easier to work on.
bobble350 said:
wedg1e said: Triumph had used a similar setup for years
Not quite, Triumphs used a slip joint in the drive shaft with the trailing arms having inner and outer pivot points to set the geometry. These slip joints are fine if they are well lubricated but can stick, then free off again coming out of a bend leading to the infamous "Triumph twitch"
But they are much easier to work on.
Don't recall such a joint on my Spitfire... but then it was 21 years ago...
Recall the handling though!
Hmmm... back to the Skoda: I recall the original Estelle design DID have provision for the driveshaft to slide in and out of the diff to a certain extent to compensate for he arc of travel... another car for 'entertaining' rear-end action!
Am I the only one happy with the handling of my trailing arm Wedge? From memory Autocar road tests didn't think there was any significant improvement when the A frame was introduced either.
The springs are so hard allowing so little movement that the lack of control has little impact IMHO. I assume the A frame cars use the same springs?
I have an article on a mod to prevent axle tramp, although I have never really found this to be an issue either.
The springs are so hard allowing so little movement that the lack of control has little impact IMHO. I assume the A frame cars use the same springs?
I have an article on a mod to prevent axle tramp, although I have never really found this to be an issue either.
Toby, IMHO your mechanics talking tosh. The driveshaft is effectively the upper suspension link, as others have said, and won't work with a slipper joint unless you spend a fortune and modify the entire back end to have an upper wishbone - doh. The current Jag XKR (400 hp) uses this upper link driveshaft arrangement! If the trailing arm is looked after, (bushes, etc) it's perfectly fine, as Danny sais. 95% of the Taz race folks use trailing arm cars. If you want to uprate the shafts to reduce time between UJ changes, Proptech (who've done the TVR shafts from the 70's) will uprate them to 400 spec (big joints) for £450 and for a more robust suspension talk to Richard at Moore racing who runs 8 (I think) Taz racers.GB
The early Taz Racers had an elliptical support piece of aluminium around the trailing arm metallastic bush. It is designed to stop the bush and pin from moving too much. I think they moved on from this to the 'U' shaped support bracket. As these only cost about £15 and the later brackets cost about £500 it may be worth doing as a cheap upgrade. I have these on my car but as it's not on the road yet I can't say how well they work.
Danny, have a look here www.moore-racing.com/images/suspension/innertrailarm.jpg
I think this is the mod. As you can see it requires mods to the trailing arms and chassis, hence the price.
The elliptical brackets just bolt on.
I think this is the mod. As you can see it requires mods to the trailing arms and chassis, hence the price.
The elliptical brackets just bolt on.
A few thoughts
On my 350 trailing arm I used 2 sets of UJ's in 9 years (not trying hard enough I hear you say). The pivot bushes also 2. I think that greasing the pin on a regular basis would go a long way to avoid it and stop it siezing and tearing the bush apart.
No racing or trials done on that set up.
I found the normal set up fine for road use.
On my 350 trailing arm I used 2 sets of UJ's in 9 years (not trying hard enough I hear you say
). The pivot bushes also 2. I think that greasing the pin on a regular basis would go a long way to avoid it and stop it siezing and tearing the bush apart. No racing or trials done on that set up.
I found the normal set up fine for road use.
I have placed a piece of pipe that fits snuggly over the bushing rubber, and protrudes slightly past the end of the rubber; I also placed a washer only slightly smaller than the opening in this tube - this limits how far the rubber is allowed to twist out of shape. This didn't significantly extend the life, but it was better longer - and upon failure doesn't go as far out of place as bare bushings.
I also changed the pins to non stepped bolts, and made the step by adding a metal bushing.
I hate the stepped bolt, I have had two snap in service. The first one that broke was siezed in the swing arm - however the second one was well greased (moly) and not siezed, it broke under heavy load on a fast corner.
History:
I had a 1981 Tasmin, I can't say exactly how many times I changed the bushes - but I think it was 3 sets by the time I hit 425,000 km, (I bought the car with 80,000km and assume it had original bushes). I changed all the u-joints once, and I believe one inner, and one outer twice.
I now have a 190,000 km 350i that I put the last 120,000km on, and I think it is ready for it's 6th set since I got it. I have changed all the u-joints, just once but only 3 needed it.
I drive the 350i very hard, including every autocross of the season for the last 3 years. I lube the u-joints frequently (although I think one pair I used had no grease fittings, so they had only been greased once - when installed).
I also changed the pins to non stepped bolts, and made the step by adding a metal bushing.
I hate the stepped bolt, I have had two snap in service. The first one that broke was siezed in the swing arm - however the second one was well greased (moly) and not siezed, it broke under heavy load on a fast corner.
History:
I had a 1981 Tasmin, I can't say exactly how many times I changed the bushes - but I think it was 3 sets by the time I hit 425,000 km, (I bought the car with 80,000km and assume it had original bushes). I changed all the u-joints once, and I believe one inner, and one outer twice.
I now have a 190,000 km 350i that I put the last 120,000km on, and I think it is ready for it's 6th set since I got it. I have changed all the u-joints, just once but only 3 needed it.
I drive the 350i very hard, including every autocross of the season for the last 3 years. I lube the u-joints frequently (although I think one pair I used had no grease fittings, so they had only been greased once - when installed).
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