+2 rear suspension bump stop length

[mbell]

Hi,

I am currently installing TTR shocks and narrow rear springs so need to replace the aeon rubber springs. Currently trying to figure out what length bump I should use.

The original aeon rubber are 80mm and I believe normally fit on a 20mm spacer (mine were missing), so total length of 100mm.

The bump stops I have bought are URO Parts 1J0 512 131C:

Bumpstop

https://www.summitracing.com/parts/URO-1J0512131C

Which are for standard fit for the rear of various VAG cars. These are ~125mm long and the TTR shocks nut has a ~7mm nut/ledge on it. So a total length of ~132mm.

From what I read on here, earlier engagement of bump stops/second spring is probably a good thing and particularly in this case where the initial resistance of the bump stop is lower than the aeon rubber spring. So I thinking that fitting these bump stops at there current length is correct thing to do.

I would be interested to know:
1) how much of the strut rod is exposed at a normal ride height on the +2 (so I can see how much travel before the bump stop would engage)
2) General thoughts on length of bump stops described above

Thanks,

Mark

[seniorchristo]

My stops are 85mm which is I believe the same length as original.

[jono]

When I did the narrow spring conversion on my last Plus 2 I played around with dampers and springs quite a bit and ended up with 13" 120lb springs and a 65mm bump stop with the Lotus alloy spacers on top of the tubes which I seem to recall are around 25mm high - this worked well and was nicely progressive in roll. A previous set up, which I aborted, introduced a sudden increase in roll resistance in bends which was very unpleasant.

I can't recall the model of bump stop but they were Powerflex and I got them from Burtons

[mbell]

Thanks Chris, Jono,

I am thinking that I'll try my current bump stops out. The initial compression of them is very light (easy with hand), so I am not too concerned about a sudden change in resistance due to them. My main concern is that there length will cause early engagement, leading to them wearing quickly and possibly reduced comfort on bumps. Then a minor concern if they will be firm enough at higher compressions.

Basic plan is to fit them and see how much free travel before engagement at sensible ride height I get and how it drives. Worse case I'll buy some shorter firm ones and swap them out.

I'll be running the TTR Fast/Comfort springs which are 12" and I think are 100lbs/in (marked 12E100). Which I think is only slightly firmer than the stock springs but much shorter.

[ill_will]

Hi Mark,

How did these Aeon replacements from URO work out in the end? I got hold of some VW items also mentioned on here but they will require a small amount of modification to fit and are potentially not as soft as I'd like initially. These URO ones, and the Superflex ones also mentioned in this thread, are also in the running.

Cheers,

Will

[stugilmour]

Just saw this thread and also curious how things worked out.

I have a collection of parts from Ray at RD Enterprises that included the adjustable perches, reduced diameter springs (marked 12” x 110 lb x 2.25” dia), and bump stops that look like these on the TTR site, which only measure 50 mm length each, with two included in a single bag.


https://www.tonythompsonracing.co.uk/pa ... spec-pair/

Based on the discussion above, I am wondering if I am supposed to use two bump stops per side to get to a total length of 100 mm? Not obvious, as I note TTR offer some components as pairs and some as single side.

Any suggestions welcome, as I sure would like to assemble everything correctly the first time!

Stu

[ill_will]

Hi Stu

I also bought some of those yellow (Spax iirc?) ones from TTR years ago, but on reading about the original Aeon design on here and comparing them with some of the VW style sometimes used (see pics in my 1967 S3 rebuild thread) these TTR yellow ones are much stiffer. I'm currently sourcing something that will give a more gradual rising rate. The yellow ones could be ok for track rate springs perhaps where the disparity in rates will be smaller.

Edit with link viewtopic.php?f=19&t=55029&start=15

The tapered end on the yellow ones I have taper internally too so I'd be concerned about it pressing against a non flat surface - I wouldn't be able to use it with the spring top caps I have without it collapsing I think but this would vary for other cap styles.

The ones I'm aware of which look suitable: Kelvedon do some that look better but possibly a bit long; there are at least two VW styles available, and there are the Superflex ones too. Have you seen any others?

Cheers

Will