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Apr 29, 2011 13:46:07 GMT
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I am now at the stage of getting the rear suspension on my Bedford Rascal sorted. Build thread HEREIt's currently at the desired ride height after fitting some Suzuki SJ rear leafs which are now down to a single leaf, some 3" lowering blocks and some custom shackles. This has brought the suspension down around 6" over 23yr old already sagged standard ride height. The biggest problem here is that one single spring (each side) is just too soft at the rear and it needs to be stiffer. Easy - fit some coilovers. This was always the intention anyway, as I have got some custom coilover struts on the front and wanted something similar on the back. The rear leaf is basically there as an axle locator because there isn't enough room to go 4 link even if I wanted to. I've already ordered the coilovers to my own specification based on the lengths of the current shock absorbers and they should be finished early next week. Spring rates aren't an issue because I can swap the springs over as many times as I like for free until I get the rate I am happy with (bonus!) I will be making new, much stronger mounts for the coilovers because the current shock absorber mounts probably won't be strong enough due to being designed just to work with shock abosrbers, not load bearing weights. None of this is a problem or a concern, I pretty much have all bases covered....except: Where the offside shock locates, there isn't enough room around the upper mount for a coilover due to the location of the fuel tank. I don't really want to relocate the fuel tank so I am going to have to use a different location for the coilover mount. Here is a shot of the current shock absorber location. The upper part, just out of shot, is where the fuel tank sits and there just isn't enough room to fit a coilover in there.... Easy - mount it the same way, same angle but from the rear of the axle facing the rear bumper rather than from the front of the axle, facing the front of the van. Here you can see a better shot of the shock absorber location. Imagine it mounted on the rear of the spring plate and going up at the same angle but rearwards (kind of mirrored to what it dows now) I could do this the other side too but the exhaust silencer is in the way on this side if I want to have the coilover facing rearward. Now, I could always rethink the exhasut system, but this is a brand new system carefully modified and fitted by BiAS, Ben, Dave, Chris and anyone else who was around the other weekend (thanks guys ;D ). It's a nice system and works well, so I don't really want to have to redesign and remake it if I don't have to. There is plenty of room on the nearside to have the coilover in the same location/angle of the existing shock (albeit with stronger mounts) My question: Is is OK to have coilovers running opposing directions on a live axle? The reason I ask is because Mitsubishi Delica's have opposing shock absorbers on the rear like so: Would it be any different to have the same type of set-up on a coilover system? Can anyone think of a reason why not? On the Delica, the shocks are the opposite way around to how I would have them on the Rascal. On the Delica, the shocks face: NS - rearward and OS - forward. If it is OK to have them opposing, would having them NS - forward and OS - rearward pose a problem compared to how my Delica ones are? Sorry for such an odd question, I can't personally think of any reason why this wouldn't work, but then I'm not a suspension expert, so would be really grateful for any input or advice. Many thanks, Bruce.
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RobinJI
Posted a lot
"Driven by the irony that only being shackled to the road could ever I be free"
Posts: 2,995
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Apr 29, 2011 13:54:11 GMT
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The issue that jumps to mind is that they'll be trying to twist the axle under compression, the right hand spring trying to push the right wheel forward, and the left spring pushing the left wheel backwards. If the axle's located well enough this shouldn't be a massive issue, but personally I'd be happier modifying the backbox for clearance to run them both backwards.
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Apr 29, 2011 18:30:54 GMT
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Thanks Robin. That was one of my concerns - putting an uneven load on the axle/spring mounts which might be fine in the short term, but could possibly cause problems later down the line through fatigue? If anyone else has any input I'd be very grateful....otherwise I might have to consider going the 'Perry Bomb' route with the exhaust which I know would make Rich, Ben and a few others happy ;D (With Dan's permission of course )
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Apr 29, 2011 19:48:21 GMT
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What I reckon you'd get is the RWD equivilent of torque-steer. Under acceleration, the rear would squirm to one side. In theory, you'd hardly notice it with such a small engine, but the Rascal is light and stiff, so it could get scary in the wet.
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Apr 29, 2011 20:58:19 GMT
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the delicas shocks are not carrying any weight, cant say its something I know to much about though.
could you not just get a custom leaf spring thats strong enough? would save work, and leafs are not inherantly worse than coils, they just lack the instant height adjustment your coil overs have, which could be sorted with some trick shackles.
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Volvo back as my main squeeze, more boost and some interior goodies on the way.
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Apr 29, 2011 21:20:01 GMT
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What I reckon you'd get is the RWD equivilent of torque-steer. Under acceleration, the rear would squirm to one side. In theory, you'd hardly notice it with such a small engine, but the Rascal is light and stiff, so it could get scary in the wet. Thanks Alan, but with the leaf springs still in place, I can't see how the axle could move enough to make this happen? The leaf springs will hold the axle straight with maybe just a tiny bit of flex, but certainly not enough to affect the way the car drives?
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Apr 29, 2011 21:34:59 GMT
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the delicas shocks are not carrying any weight, cant say its something I know to much about though. Yeah, I know this, I mentioned it above about load bearing etc....when referring to the mounts and uprating them. It's not the load bearing side of things I am concerned about because I'm changing the mounts to something much more suitable. It's the geometry thing I'm asking about. could you not just get a custom leaf spring thats strong enough? would save work, and leafs are not inherantly worse than coils, they just lack the instant height adjustment your coil overs have, which could be sorted with some trick shackles. The thing there is the 'one shot' chance to get some custom springs made. If I get the springs the wrong rate (which is pretty much anyones guess) then I'm either stuck with them, or having to pay out for more springs at ?? cost and more time & effort. Having the coilovers allows me FREE changes of springs until I get the rates I am happy with. I doubt a leaf spring compay will do that for me? Plus the whole rear coilover set-up is costing me £160 - that's new coilovers with the option to change spring rates free, adjustable dampers and the facility to adjust the height. How much would a set of custom leaf springs be? Plus they are far too much of a gamble in order to save what is some fairly simple fabrication work to get the coilovers mounted. I'd rather do the extra work for the mounts than risk getting the wrong leaf springs. Also, if you've looked at the build thread, you'll see I've got custom adjustable shackles which are currently set on the 'as low as possible' setting where any lower and the eye of the leaf would hit the body mount. Coilovers it is, regardless.....I've already ordered them and they will be going on. I just wanted to see if anyone had any exact or definitive reason (not speculation) as to why the opposing coilovers would/woulnd't work. Many thanks for your input so far guys.
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Apr 29, 2011 21:36:43 GMT
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From what I can remember the Ford 100E has the same setup, and it didn't give me any problems, but that was with 36bhp! That said, many people fit Anglia 105E axles to them by using the 100E spring seats (the shock mounts are integral to the spring mount) and then proceed to run Pinto power through them, so I reckon that providing the mounts are suitably beefy, you should be OK. Have a word with Kev(aceadvice) as he's had plenty of experience with hot 100Es.
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1953 Minor (Long term project) PT Cruiser
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CIH
Posted a lot
Posts: 1,466
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Apr 29, 2011 21:48:17 GMT
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What I reckon you'd get is the RWD equivilent of torque-steer. Under acceleration, the rear would squirm to one side. In theory, you'd hardly notice it with such a small engine, but the Rascal is light and stiff, so it could get scary in the wet. Thanks Alan, but with the leaf springs still in place, I can't see how the axle could move enough to make this happen? The leaf springs will hold the axle straight with maybe just a tiny bit of flex, but certainly not enough to affect the way the car drives? No that's the main drawback when leaf springs locate the axle. They're just not very go at doing so.
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Apr 29, 2011 21:53:36 GMT
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Thanks Alan, but with the leaf springs still in place, I can't see how the axle could move enough to make this happen? The leaf springs will hold the axle straight with maybe just a tiny bit of flex, but certainly not enough to affect the way the car drives? No that's the main drawback when leaf springs locate the axle. They're just not very go at doing so. So you're saying there will be enough flex to create rear torque steer? Is this with or without opposing coilover set-up? (before answering, please remember this is a 44hp 1 litre stock engine etc...) Please can you clarify your comment with specific regard to the set-up I am looking at fitting.
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Apr 29, 2011 22:06:40 GMT
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p100's run the same mount method as those one, but are alot beefer, might be worth a check.
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Apr 29, 2011 22:31:07 GMT
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leafs are not that bad at axle location fore and aft depending what bushes are fitted to them at the front, sideways is an issue, hence panhard rods, they also suffer from wind up causing axle hop, but again thats fixable with anti tramp bars.
i wasnt questioning your engineering skills when i mentioned the shocks not being weight bearing, i meant more that if you offset your coil overs, which ARE load bearing, that may have strange effects on the handling.
the other issue you will have is that the leaves will want to make the suspension describe an arc as it loads and unloads, while your coil overs will want it to go up and down in a straight line and you might bend them.
you can make "slipper springs" to get round that, but then you need links to locate the axle so your no better off.
i think if i wanst sure id be making a scale model just to see what it felt and looked like as it all moved about.
what about losing the leaves, and making lower links where the leaves were, and making the top links like a mk5 cortina, or use a single 3 point top mount like on a vitara, both of those get away without using a panhard and both are more compact then running a proper paralell 4 link.
cant remember how much room there is under the floor in the middle of a rascal.
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Volvo back as my main squeeze, more boost and some interior goodies on the way.
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Apr 29, 2011 22:40:34 GMT
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(before answering, please remember this is a 44hp 1 litre stock engine etc...) a standard 1100 mk1 escort can get the axle bouncing up and down, they cant have much more power than that and they are not running extra soft leaf springs, the 86bhp 1600 mexicos had anto tramp bars as standard, if that helps.
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Volvo back as my main squeeze, more boost and some interior goodies on the way.
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B-8-D
Posted a lot
down to one car!!
Posts: 4,038
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Apr 29, 2011 22:42:35 GMT
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bruce the shocks are usually mounted in lots of leaf sprung live axle stuff one behind and one infront as it was found to reduce axle "hop" its where the axle twists as an opposing reaction to wheel direction when accelerating. if the wheel then looses traction momenterily the axle will spring back, this can happen over and over causing this "wheel hop" its found that siting the shocks (dampers) front and rear reduced this significantly.. I think it was chevy that were among the first to emply this idea?! so for shocks only this is a good thing.
however you are thinking of using coilovers in these placements right?
I doubt it would make much difference to be honest as long as the are slanted the same away from the axle std movement either way so as its rate (actually a loosing rate) will be the same.. BUT:
the problem is that the axle doesnt just move up and down virtically. the leafs will dictate a sort of arc that is hard to determine acurately as the shackle will move as the leaf strightens both front and rear of the axle line but only moving rearwards as the suspension compresses (I'm assuming the shackle is at the rear?) so it will move in an arc so the rear leaning shock will be effectlivly acting anything from a higher rising rate (or even less of a loosing rate) than the front.. for a van not driven too hard it may not be noticeable but really its not ideal.. so id say if you can get them both one side of the axle then do so (if using coilovers)..
my 2p si
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Last Edit: Apr 29, 2011 22:49:48 GMT by B-8-D
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stealthstylz
Club Retro Rides Member
Posts: 14,873
Club RR Member Number: 174
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Apr 29, 2011 23:16:58 GMT
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I don't think you'd notice the difference, its not something you're gonna be thrashing the knackers off. Yeah it might tramp more, but 1100 Escorts only tramp if you really give it some stick. You'll just not have to boot it of the line lol.
As another suggestion i'd bin the leaf springs altogether and run ladder bars to the front spring mounts. It's not difficult to do, and you'll gain much more ground clearance and scrubline.
Matt
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Thanks for the comments guys - lots of useful info there. Matt & Pop-up, I'd love to run some other type of linkage, but there are a few issues which prevent that: If I was to ditch the leaf and run a ladder bar, the distance from bottom of axle to body mount is only about 7" which means needing coilovers that can compress to around 6" which Pro-Tech cannot make. The extra distance gained from the lowering blocks and spring plate allows me to run a more suitable sized coilover. Unless I run a panhard rod, which I really don't want to because I don't like the way they can move the axle side to side - especially when the wheels are only mm's from the sliding door anyway, the only other options are a top yoke like Land Rovers and Vitaras have...but there is simply no room (I've got around an inch of travel before hitting the floor! That's without adding any mounts to the top of the diff) and the only other viable option is a watts linkage, but again, it's finding room to get it all mounted. Scrub lines, despite how they might appear, are actually fine. We checked them all the other weekend and everything clears. Si, thanks for the comments. I'd kinda figured the opposing shock idea was some kind of anti-tramp but what concerned me was the thought of reversing the way they are mounted, (i.e. the opposite way they are fitted to the Delica) which in my mind could possibly actually promote axle tramp rather than minimise it?? Seeing as the coilovers are ordered and paid for, I'll be having to use them anyway. Based on the comments about opposing movement it looks like it's going to be best to mount the coilovers on the same axis, therefore I will be moving the mounts rearwards on both sides and modifying the exhaust. I'm not worried about leaving the springs in, marginal axle tramp or lack of fancy rear suspension systems. If I want to do hard launches, wheelspins and the like I would rather do it in the MX5 (or Delica as some have witnessed ). The Rascal is purely for bimbling around in with a big smile on my face.....although even with the 3" blocks and single leaf, it still managed to do quite a good wheelspin out of the unit onto the road the other day - no judder or jumping.....nice and smooth all the way ;D Thanks again for all the input guys, very very helpful.
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speedy88
Club Retro Rides Member
"Nice Cortina mate"
Posts: 2,281
Club RR Member Number: 118
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As above I don't think you'll notice the difference much. If its anything further you need, I have absolutely no tramp bars on my NSR and I drive balls to the line pretty much every day ;D
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even with the 3" blocks and single leaf, it still managed to do quite a good wheelspin out of the unit onto the road the other day - no judder or jumping.....nice and smooth all the way ;D Doesn't look much, but I was proud of it from my 44hp little van which was (at the time) running rough on 4yr old stale fuel ;D ...and that was without even really trying.
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Could you mount the tops in board, ie turn the bottom mounts 90 degrees and move them rearwards to behind the axle then run the coilovers at an angle 30 degrees or so and mount the tops inboard. I had an sj410 with this conversion, then to give more movement from longer shocks but it could work for you if there's enough space.
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gazjon
Part of things
Posts: 632
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Was pondering your problem and wondered if you could use a similar idea to what some of our buses use at work. It basically comprises of two parallel steel bars bushed at one end. The bars are joined togehter by a transversly mounted plate which also locates the panard rod to the body. The axle sits infront of this and is bolted to the parallel arms using a traditional U-bolt/sadel setup. From the rear parallel arms to the body is where the airbags locate. But i see no reason why a coilover setup would not do an even better job. Will try and get a picture if you want, but its like these photos below. Hope that makes some kind of sense. Gary
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Mk2 Cavalier saloon Mk4 Astra Van z20let
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