mk1 front suspension travel.- UPDATED WITH PICS.

Couple of questions, following on from the tracking and geo thread, i've also been thinking about the limited suspension travel on lowered mk1's.
I know Mr Hillclimber has got extended top mounts (?) and the white mk1 that i now think is owned by somebody (on here?) up in Scotland has had the turrets extended.

Jason, what difference did you notice after doing it, just better damping response or were you actually bottoming out. I know my travel is limited as the solid topmounts sit a 1"ish lower than standard topmounts already, i dont think the spring is bottoming out but the damper is working at end of it's travel.

I was thinking of spacing the topmount (solid ali eccentric in my case) up ontop of the turret with some wooden spacing blocks and then bolting through the whole lot together with say 4-6 bolts alround. Similar to the method here from vortex. But only the turret part, not the strut part.http://www.ghiagirl.com/phrankentruk/struts.htm

Thoughts pls any obvious negatives....
I don't really want to get the turrets cut and rewelded and i like the idea that it's reversable.

 

I would machine them up out of a lump of solid aluminium. i think H&R also make super short coilovers too however, this is an expensive option. Couldnt AVO rebuild your shocks with shorter damper rods?

Gurds

 

If your car is lowered but your damper is reaching the end of its travel, then you've got the wrong shocks fitted to it. So you need to replace with shortened ones.

As far as the altered top mount is concerned, no real issues so long as its strong enough (I'd have used more than 4x little bolts though!). Remember when you go really low, there are other considerations like the wishbones being at an angle they were never designed at, and the driveshafts and track rods possibly contacting the bodywork.

 

PaulC, Ian wouldn't have this problem with standard topmounts. It is because Ian is using sloid topmounts that sit inside the suspension turrets that in turn move the top mount position at least 1 inch lower than standard. This in turn raises the car by the same amount requiring the coilover to be wound down even lower to sit at the same height with the standard topmount. Hope that made sense? This is why Ian wants to space the topmount in order to retrieve the previous damper length.

Gurds

 

Yep gurds is right paul, i don't run the car that low anyway, but using solid top mounts shortens my travel further.

Avo probably could, but that will cost money as will machining them from ali , also the stress will be on the bolts used to secure the mount and spacer rather than on the spacer itself, as any shock loading going through the wheel will try to seperate the mount from the spacer and turret, so i think wood will be perfectly suitable if a bit pikey looking. I'm more concerned if 4 x m8 12.9 bolts each side will be strong enough to take load and stress. I am dubious.

 

I was thinking along the lines of these:
http://www.pmwltd.com/gallery.html

Dont look cheap though. Gives you an idea of the number of bolts that may be required.

Gurds

 

I'd definately consider fitting shorter damper rods over the other option, for the sole reason it's a proper job. How much would AVO charge for fitting shorter rods? It could be money well spent. I've heard this reduction in stroke (oo-er) technique on quite a few Japanese motors.

Wood with suspension components... Royal Oak? Mahogany? Are you having a laugh? Aluminium or not at all imo.

They look substantial Gurds . The Mk2 in the VW Cup runs something similar I think, with a thick ally plate and camber adjustment.

 

Yeah, i'd spotted those the other day gurds, nice looking bits of kit, it was what got me thinking about this again. But like you say 's amd still only 6 bolts thou.

James, not having a laugh at all, Aren't morgan chassis's/frames still made of wood???

The wooden spacer would only be sandwiched between my ali topmount at the top and the steel turret at the bottom, and it'll only be in compression from the bolts holding it all together, so any hard wood would do! All the suspension force would be trying to pull the bolts apart rather than compressing the wood, it will only be under rebound that the wood would be compressed. (few too many would wood 's there!)


Yes there are definately better ways of doing it, but not for free and not so easily reversable, i'm selling the car early next year so don't really want to spend any more cash on it, but i'd still like to continue developing it.

 

Well in that case, the wood might well prevail for the time you have with the car. I'm sure I have seen those ones G has in that link on recent touring cars, remembering that they are a lot, lot stiffer, jumping over kerbs, rutted grass etc.

It's nice to see how you're developing the Mk1, I've been reading with interest these past years. Top work and top Mk1.

 

I've got you now. What's the reason for going with solid top mount (I think I saw the thread on Mk1 suspension geometry) - is it so you can set the castor and adjust the disatance between steering pivot and wheel centre (can't remember the name for that dimension).

In this case, I'd go for custom shorter dampers, or raise the car a little higher. I've noticed most racers tend to run around 50-60mm drop, while slammed cars on coilovers typically go as low as 60-100mm. The coilovers will have a range they're approved to run, I think its typically 75mm drop. So if you lowered 50mm and the solid mount added 25mm, you'd be okay. But any lower, you'd need to seek new dampers.

I'd be really wary of cutting the top of the strut and extending it upwards. If you hit a large bump and bottomed out your suspension, then you'd probably pull the bolts through the top of the bodywork, leading to instant collapse at that corner, rather than allowing the body of the car to take the load (possibly bending, but leaving the car on its wheels able to roll).

 

i got the solid top mounts primarily because i kept knackering standard top mounts with the stiffer front springs i use, but also so i could adjust the castor, camber and scrub radius.

i think i might just be okay with the height where it is at the moment, but i've now got rose jointed trackrod ends and i'm making some ball joint spacers so i could hopefully go a bit lower and still keep a reasonable roll centre, hence the thought really. i would not cut the top of the existing turrets but instead mount the spacer directly on top, using a snug fit against the top lip to help ward against any lateral movement and then probably make up a new top strut brace after that, as i've not had one fitted at all since going to the ABF block (not enough room).
For sure shortened rods are the better solution but that's not happening due to cost. The strength of the bolts and speading the load around the turret are key thou. You're also right strengthwise, i'm still not convinced that it will be strong enough when crashing over kerbs etc. Thats one reason i wouldn't cut and weld an extension in the turret, i don't trust my welding and won't pay anybody to do it for me..

 

Mmmm, maybe fitting a relief ring under the turret to spread the load a bit. ( A 5mm steel ring that acts like a big washer with the 6 holes drilled in it).

Gurds

 

16valver

 

I noticed just by looking under the arch that there was'nt much of the damper rod sticking out of the top. So when I changed to the Bilsteins & coil over set-up i thought some extra damper travel wouldnt hurt, especially as I wanted to lower it more. The top hat section of the Bonrath mount that I use were cut from the plate section with the bolts in and a strip of steel, about an inch, was welded in. I've had "no"problems with these mounts in three years of competition use (I think you've seen the pics ?).

I dont see a problem with mounting yr top mount on the outside of the tower. I've seen many top competition cars like that (BTCC, WRC included) and know a chap down here in the southwest who used to run just a set-up on his 205, one of the most successful mod-prod saloons in recent years, plus he's a real suspension boff and would'nt do it if there was any danger. Obviously decent bolts are a must.

I'm looking into some alloy top mounts soon with the top hat section extended, if they turn out ok then I may make them available for sale.

I must admit, I'd go with an alloy spacer extension but the right wood would (!) no doubt do the job.

 

I'd be tempted to get a couple of ally ones machined up but I'm sure it wont make any difference. I think Morgan use summat like Ash for the frames but as you are cutting a ring of it I'd try marine ply to stop it splitting down the grain. Its tough as old boot so it should be pretty resistant to the abuse and fairly water proof too. Sandwich 2 bits together with Cascamite (sp?) if you need more thickness. Dont forget a lick of creosote (you were waiting for a cheap joke like that I'll bet...)

 

Yeah i probably would varnish it!

 

There was a fapping fast 911 turbo - flat nose thingy - at snetterton last year. Turned out his front splitter was made of marine ply as it was getting too expensive replacing the carbon one when going over the curbs !

 

4x 12.9 M8 socket head cap's sould be fine, just done a bit of fag packet maths and thry should hold it. only way you may find they would fail is in fatugue but this would be be over long period of time so just replace the bolts periodicly.

Even taking in to account a weight being dropped on to it providing the thread dosent strip an 8mm bolt will hold 1200Kg before it breaks, so 4 bolts will comfortably hold the 300kg corner of the car.

Just make sure you get some high quallity nuts is ideally tap them in to something atleast 20mm deep. and don't over tighten them when you nip them up. 40 NM ish i would think

 

Yes but that's at static. You need to think of dynamic loads. I am thinking of a situation, for example avoiding a child who runs out into the road and forces you to hit and mount a kerb at 40mph or so. I reckon you'd put 7-8g through the top mount of the car in this scenario. Add in a safety factor of 1.5, and we're talking 12g - so 300kg feels like 3600kg. Quite close to the ultimate load of the 4x bolts at 4800kg.

 

No i did take in to consideration the dynamic loading, i assumed a 300Kg corner weight being dropped from 1m which should take in to consideration even the most ambitious kerb use.

Did some tensile testing the other day at uni and a lolly pop stick will hols a load os 2300N before it failed, that's arround 230Kg's, It's verry supprising just how strong some materials are in tension.