It's a question of length .................

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varleym
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Full Name: Mark Varley

It's a question of length .................

Postby varleym » Wed Jun 08, 2011 11:45 am

Having now fitted the 200+ lbs of Devon bumper and 8274, I've only got about 3 inches of compression travel on the front suspension ie. between the axle and the bump stop. I've got around 5 inches at the back.

The springs are medium weight +2's and the dampers +5's. I've also got extended turrets (+2's) on the front and extended bump stops all round. By my reckoning and also after speaking to Adventure 4x4 in Leeds where I got all my suspension from, I should be able to go back to standard height bump stops at the front, thereby getting another 2 inches or so of compression travel, without any ill effects. Just before I do though, I wanted to check this out with some of the more 'seasoned' members. All the kit is Terrafirma by the way.

If anyone knows of any just impediment why I may not undertake the modification above please say so now, rather than waiting till the top of the damper comes through the bonnet on a trial and say 'well I wouldnt have done it like that' !!

Seriously, any comments welcome.

Cheers

Mark

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davew
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Full Name: Dave White

Postby davew » Wed Jun 08, 2011 1:51 pm

The whole +2, +3, +5, -2 rating thing is completely trivial, it gives no indication at all regarding the actual height or capabilities of the suspension. Personally I'd ignore the salesman's drivel and actually measure the components myself.

The only reason for fitting extended bump stops is essentially a bodge job to try and compensate for ill fitting shock absorbers which don't have internal bump stops.

The question has to be, why did you fit extended bump stops in the first place ? If you needed them to start off with and you haven't changed any of the suspension components then you still need them now.

You can calculate the necessity or otherwise of the extended bump stops by removing a shock absorber and taking a tape measure to it and the vehicle.

Measure the fully closed length of the shock absorber and then measure the distance between the top and bottom mounting points. Work out how much further up the axle can travel from it's current position before it would hit the chassis and subtract that from the mounting distance.

Any difference (assuming the closed length is longer than the mounting distance) is the minimum length of bump stop you require. Bear in mind that in heavy impacts the bump stop will compress quite a lot so you should allow a safety margin, especially if the shocks don't have internal stops.

The actual ride height of the vehicle has no effect on the requirement for bump stops unless the spring gets coil bound before the shock absorber bottoms out, in which case you're likely to damage the spring.

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varleym
Posts: 413
Joined: Wed Feb 17, 2010 4:42 pm
Location: Harrogate
Full Name: Mark Varley

Postby varleym » Wed Jun 08, 2011 4:25 pm

Thanks Dave - comprehensive answer as ever.

The truth is that I probably fell into the trap of fitting the extended bump stops not because I'd worked out I needed them but more down to 'anecdotal' stories from people who were no more informed than I was and also a bit of 'spin' from the sales guy! My only excuse is that I was young and nieve (well nieve anyway!).

So let that be a lesson kids - do your homework and take advice from those who know, not those who think they know. Oh and don't take sweets from strangers either !!!

Cheers

Mark

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Matthews
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Full Name: Matthew Sykes

Postby Matthews » Wed Jun 08, 2011 8:42 pm

Just to confuse you even more I run standard length shocks and bump stops but have chosen springs to give me the correct ride height /loading and altered the shock mounts to suite, i.e lowered them by a carefully measured/calculated formula and tapemeasure to allow for maximum downward travel without bottomming out the shocks, most extended shocks have very little if any greater travel than standard so are a pointless excercise apart from making someone some money.
Matthew


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