Bottoming out

Bottoming out

Author
Discussion

Bull McCabe

Original Poster:

244 posts

251 months

Saturday 5th May 2018
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I have a 2500 running on adjustable AVOs all round, double springs and dampers on the rear.
I bought the car last year from an area of the country with better roads, so when I got driving on local roads the silencer in the middle of the car would bottom out on poorer surfaces. I wound the dials up on the shocks, which reduced the frequency of the car bottoming out, but this was at the cost of the ride being very harsh, which meant having to rapidly reduce speed when hitting a slightly uneven stretch of tarmac. Cars following on must have thought I was suddenly running on one cylinder as they glided along what seemed a smooth stretch of road.
I have recently raised the ride height and softened the shocks, which has made a huge difference, the changes in road surfaces are barely felt and the car is a much more pleasant ride, but it looks slightly odd riding higher. The flat corner plates of the chassis are 160mm from the floor. I will say that although the car is much more relaxed on poor roads, it feels slightly less precise and taut on a nice A road.
Reading through the history, a previous owner (from about 20 years ago) had written a letter to the next owner. In this letter he mentions that he cut the silencer out to solve the problem of the silencer hitting the tarmac, he actually says he liked the sound the car made without the box. Obviously, at the time the car didn't have adjustable suspension and this solved the problem.
I am wondering if I can find a happy medium of reasonable ride height, handling and comfort if I remove the silencer, lower the height and have the shocks somewhere in the mid range.
Will the noise of running without a silencer be too much to bear or should I just try to reach a compromise by making adjustments until I find the best settings for me?

Edited by Bull McCabe on Saturday 5th May 23:32

Over50

64 posts

184 months

Monday 7th May 2018
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Hello Bull, I do remember my 1800S in the early 70's would hit the road on uneven surfaces, so much so it was called clanger . Move on nearly 50 years, when my Vixen was refurbished the new exhaust was rerouted to be as high as possible. Also running Avo's, no problems even with our potholed riddled roads.

280i

160 posts

152 months

Monday 7th May 2018
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I have a Vixen 2500 as well. My car also bottomed out quite a bit until I addressed it. I would first start by putting a level on the front wishbones. I set my car so they were parallel with the road. I then did the same with the rear of the car. next I adjusted the rear up a bit so the car would have a 3/4 rake (higher in the rear measured from the outrigger to the ground in front of the rear wheels. The cars stance now looks good and the car does not bottom out.

Let me know if you want any specific measurements as I would be happy to do so.


Bull McCabe

Original Poster:

244 posts

251 months

Monday 7th May 2018
quotequote all
Thanks for the replies,

Over50, my exhaust is set as high as possible. There is minimal clearance between the chassis and the exhaust. I could try to alter the brackets for the rubber mounts to try to get it as high as possible, but I don't think it would take much before the exhaust would vibrate against the chassis. I will look into it next weekend though, because half an inch could make a big difference.

280i, yes, perhaps some more details would be good. It's a shame I only saw your reply now, as I had the car up on the lift earlier and could have taken some pictures. I know the car has had some suspension upgrades in the past, so perhaps I could post some photos up as soon as I get it back on the lift. I will try the level on the wishbones and let you know. I will post up some more info soon.

Thanks again

plasticpig72

1,647 posts

149 months

Tuesday 8th May 2018
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What tyres have you fitted and is the rolling dia smaller than the original size tyres.
Alan

Bull McCabe

Original Poster:

244 posts

251 months

Tuesday 8th May 2018
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Alan,

I am running 185/65/15 at the moment. The car was running on 165/70s but they were 15 years old and far from confidence inspiring in the wet. Many sections of the local roads are poor and don't have camber to allow the rain to run off, so it is not unusual to find standing water so I was keen to put some new ones on with a decent wet rating. The car bottomed out on the tyres I got it with, which is why I firmed up the shocks. I was just fishing to see if there were any tips I could pick up. I have since wound the height down again, to a mid point and firmed the shocks slightly and it does seem a slight improvement. I will just keep fiddling to try and find the optimum.
The exhaust system is a Heath Robinson with the 2 silencers welded in, so I can also have a look to see if I can find silencers with a shallower depth.

Thanks again for the replies.

plasticpig72

1,647 posts

149 months

Wednesday 9th May 2018
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On my 3000S i have a stainless system and on the boxes thick skid plates have been welded on them, running on 185 original size.
On my 3000M i am running on 205/70 (at 2 bar) so the rolling dia is just a very little smaller than the original 185 and does not bottom on the road.
The 3000M drives better imho.
Alan

ATE399J

729 posts

237 months

Wednesday 9th May 2018
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Original fit tyres were 165 full profile so you are loosing some clearance by reducing the radius of those you have fitted.
I find I have developed strong buttock muscles - a lot of clenching when the car bottoms out!

anonymous-user

54 months

Wednesday 9th May 2018
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ATE399J said:
I find I have developed strong buttock muscles - a lot of clenching when the car bottoms out!
I have just discovered the reason why my buttocks feel numb after an hour driving the Vixen - the springs and dampers are ex Lotus Exige at 385lb. Yes 385!
I’ve been driving it for 4 years like that too.
Bottoming out doesn’t happen, but a change is in order

Edited by V6Pushfit on Wednesday 9th May 19:01

the other tim

136 posts

147 months

Saturday 12th May 2018
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165x15 oe tyres 26", 185x65 24.5", I would imagine you've lost some compliance with the low profile tyres too

GTRene

16,543 posts

224 months

Sunday 13th May 2018
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or do like this guy did and some others as well, give them side pipes :-)






ATE399J

729 posts

237 months

Sunday 13th May 2018
quotequote all
GTRene said:
or do like this guy did and some others as well, give them side pipes :-)





No, No, no nono, no... please, no.

Andrew Gray

4,969 posts

149 months

Wednesday 16th May 2018
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We have yet to bottom out once in 1200 miles on the trip we are doing and we have a middle box well be it very tight up to the chassis its mm away from the chassis and gear box just enough so it does not fowl anywhere.
It can be done without the ride being to high and that's with two people luggage full size spare wheel and some emergency spares in case we brake things.

[url]|https://thumbsnap.com/QpNcdAfB[/url

Andrew