Lower Rear Control Arm Mount Issues

[ultima_ontario]

Hope all are well folks!

It sounds like earlier model GTR's with sticky tyres and higher HP motors had problems bending subject

I had mine fail last week - rear, right, bottom, front A-arm mount ripped off (weld didn't fail - the tabs / bracket did) under mild throttle application on right hand turn into straight on track. I fully inspected 6 laps earlier and no off track damage / impacts

Upper shock mount bent as well

Photos attached - 2nd photo is healthy opposite side (left - how it should look)

Bolts were all torqued to spec and I paint marked for visual verification between sessions

Thinking I need to order new mount(s) from Ultima, new brake line etc. What do you recommend?
Just went though the build manual and don't see any original chassis alignment specs or material details - would appreciate chassis thickness, material, alignment specs so my local race shop can prepare to repair

[Steve_D]

For cars used the way you are the Factory offered the caps that go over the mount which I can see you have. The chassis tube will most likely be ERW tube with a wall thickness of 1.5 or 1.6mm they may be 2mm but I very much doubt it.

The Factory will most likely just say 'it's a road car and not designed to run slicks'. In fairness that is all any manufacturer would be able to say.
Earlier comments about this ran along the lines of those brackets being sized such that a corner impact would allow the suspension to part without destroying the chassis.

Your fabricator has all the dimensions they need by looking at the other side. All that will remain is for you/fabricator to decide what material thickness to replace them with. Currently they will be 3mm thick so 4 or 5mm should do the job. In place of the caps I would suggest welding a brace to do the same job with the addition that it can also be welded to the chassis tube.

Steve

[Steve_D]

Further thought try talking to MacG Racing ( https://www.macgracing.co.uk/ ) who will most likely already have been where you are as they race an Ultima.

Steve

[845ste]

real incredible!!!
with slick or semi-slick?

[GTRMikie]

The GTR was designed to be a road car, not a race or track car.

[UltimaCH]

This topic was discussed some time back (several years probably) and it seemed that the tabs bent when doing dyno pulls

[GTRMikie]

I always thought those lugs looked rather flimsy considering the power that is transmitted through them. But I have complete faith in Ted Marlow’s engineering skills.

[deadscoob]

GTRMikie said:

The GTR was designed to be a road car, not a race or track car.

Well as the origins were founded from early race Ultimas and it’s stated the chassis is capable of handling 2000hp engines, it’s reasonable to expect that not too happen still surely?

[LuckyP]

Ahhhh.. takes me back.