Hi all,
I had a windfall from the tax deparment this year and want to waste the money on my Sierra!!
It's my only car, and I intend to use it for 4wd touring around Australia and for weekend trips that I do from time to time. Most of you will think I'm stupid trying to get 31's under it given that for my purpose I don't really need them, but what the hell I've got the money and a Sierra on 31's looks awesome you must agree.
The only thing I've got so far is a luggage rack fixed to roof.
To get 31's running smoothly under it I've worked out that I'll need to hammer flat the seams in the wheel arches and move the front bumper outrigger. That should be easy enough.
I decided that I didn't want to cut guards or do a body lift, so that left me with the option of a spring lift (40mm OME) with bumpstop spacers/extensions. Someone suggested to me that 50mm spacers in the front should be sufficient with no rear spacers and I'll clear these tyres. Has anyone actually run this setup, or similar and if so what shocks did they use, and how did it perform? I'm not into the idea of commodore/hiace shocks from gabriel as it sounds like they're not much improvement on the factory shocks, and I'd be willing to shell out for something good quality. I've read that Jr. Zook (from the auszookers board) is very happy with his Koni 80 series rebound adjustable shocks but I'm unsure what lengths to buy and if they will work in my rig without the need for custom fabricating mounts. I'd prefer to go for something that bolts in to the factory setup. Advice is welcome as I've read through a lot of threads on this issue now and can't find the solution I'm after.
Hi David. You've reminded me I owed you a PM on AZ, but as you've posted the relevant information on here, I'll respond here rather than on AZ.
Finding longer shocks that bolt in to the front of a Sierra is a significant challenge. It's not the physical dimensions that are the problem, it's the valving. Sierras are a very very light vehicle, even by road car standards, and also run leaf springs, which have their own damping (called "internal friction.)
Add these two things together and the result is a shock absorber that needs to be incredibly softly valved. In fact, it's possible to remove the shocks entirely on a Sierra and the car remains surprisingly drivable - that's how little they are doing.
I think that standard OME Sierra shocks are already borderline too stiff, and that's because they are really designed for a car that's quite heavily laden. In an empty Sierra, I think they are quite choppy. Finding a bolt-in longer fitment from the OME catalog that's as soft as the Sierra valving is almost impossible. I fitted quite a few long OME shocks (Part # N76) but these are a race buggy fitment and are designed for multiple applications, (OME recommend up to three per wheel in a light race car!) They are extemely long and require custom mounts. They also generally end up fouling the tyres because of how tall the mounts end up and how large the shock absorber is.
OME's are mass produced "sealed for life" shock, so there is no possibility of modifying them.
Koni's are excellent, and as they are rebuildable, you can have them valved to suit. I have been in a car running OME springs and Koni shocks, and I recall being very impressed with the ride. This was nearly 20 years ago though, so it's hazy - we are certainly running our cars softer in the spring now than back then, so maybe my recollection is a bit irrelevant. The car I am recalling also had no bumpstop spacing, so it had ample compression travel, which gives soft shocks more chance to work. Reduce that down with bumpstop spacing and you'll need a stiffer shock to prevent the axle from smashing through to the bumpstop too easily.
In any case, the cost of Koni's and custom valving is, in my opinion, unjustifiable. Remember, this is a car that drives quite well with the shocks removed altogether so spending $500 or more on a pair of shocks just doesn't seem to make any sense, and it's why I find it easier to justify making mounts to suit a very long, very soft, "cheap" shock (in an OME N76) or recommending a cheap bolt in (Commodore Gabriel) which I ran myself for some years.
So, in short, will you find exactly the solution you're after? Not really. You're starting with a compromise (31's an no guard cutting/body lift) so that's going to restrict the effectiveness of what you can achieve with the front suspension from a ride/travel perspective. I'm going to add that if your primary reason for 31's is cosmetic, and your use is easy driving and touring, you might be a bit dissapointed with the compromise they introduce. I think they are an excellent choice for a Sierra, but I'd add that's with the use of a BL or guard cutting, and generally with non-reversible suspension modifications.
It's a complex issue. Perhaps it's worth seeing some member's cars work off road and making some comparisons before you commit to a build path.
Steve.
michaelpiranha2000 wrote: The rear is in great condition. but has a broken crown wheel and pinon
Thanks for the reply Steve.
I agree it would be great to try out some different setups before I start the build, and I will try to do that in the near future. Unfortunately the guys arranged the Fryers Ranges trip on a day I am working, but there will be other opportunities soon I'm sure.
For the time being I will continue to gather information on setting up the suspension. At the moment my dilemma is that I can't work out what length shock absorbers are required for my build. I know I want to use OME 40mm lifted springs in a standard configuration with the rear springs in the rear, and front springs in the front. If I don't use B.S spacers in the rear then I'm assuming I can go with whatever normal duty shock absorber ARB are selling in their Sierra setup, correct??
Also, if I use 50mm B.S spacers in the front, does it follow that I will require a shock that is 50mm longer than standard?? Is that how simple the equation is, or does increasing the height of the car at rest by 40mm (using the longer springs) also play into this equation??
Correct, if you don't use any bumpstop spacing, the standard OME shock is fine for the rear.
In fact, there is almost nothing to be gained from adding a longer rear shock, even if you need to add bumpstop spacing - the standard rear shocks don't limit the down travel available, so adding longer ones is work for the sake of work in my opinion. The springs limit the travel in the rear only just after the standard shocks run out of travel.
If you add front bumpstop spacing, you don't require longer front shocks, the spacer just means you are able to fit them without custom fabrication. There is a (little) more droop available in the front springs that can be gained with a longer shock, but there isn't 50mm of extra droop in the spring that can be recovered with the longer shocks.
No, the sprung height of the vehicle doesn't matter at all - that's just the rest point in a range of motion. The extents of the range of motion are dictated by the bumpstops (at compression) and the shock length (with standard shocks) at droop. With a longer shock installed, the extent of droop will be the spring - there will be some shock travel unused. You will gain about 20mm of travel, so all up you've "lost" 30mm of travel overall by adding the 50mm bumpstop spacers.
In relation to the front, it all really comes back to the shock valving. If you want the best valving possible, you'll need to keep OME shocks and live with the lost droop, have custom Koni's valved for your application, or make custom mounts.
If you're willing to accept a small reduction in ride quality (over what was possible, not what you have now) you can bolt in commodore shocks and call it good. They're cheap and effective. Compared to the cost of a custom Koni, you could buy Gabriel commodore shocks and OME shocks and compare them and still be in front.
Steve.
michaelpiranha2000 wrote: The rear is in great condition. but has a broken crown wheel and pinon
Thanks again Steve.
Well I'm pretty much decided on the suspension setup then. Sounds like OME standards will be fine in the rear. Only question is the shocks for the front. I'm still thinking to steer clear of the Gabriels and go for something with softer valving, to match the OME's which will be in the rear. I found these Koni's being sold by an Aussie company (Climax Suspension) which are being marketed as suitable for a Sierra with 0-35mm of spring lift. They might just be the ticket to a softer ride?? I certainly wouldn't be averse to spending an extra $280 over the Gabriels (which are $100 pair) as I want the car to be comfortable for long trips with a passenger in the front.
80-2275Sierra
80 SERIES Adjustable Twin Tube Hydraulic
Koni
Shock Absorber
Front
Pack Contains: 1 Pair
$380.40
Problem is I have no idea how to work out the mounting compatibility or whether the length is appropriate. I checked the Koni website and no such information is available. Might have to call Climax Suspension tomorrow and get some specs on these.
Anyone have any experience using this shock in a Sierra??
That shock is likely to be exactly the same length as a standard Suzuki front shock. It certainly won't be any longer than an OME front shock, but a lot more money.
Don't confuse lift with bumpstop spacing. A "lift" shock for a leaf sprung vehicle can't really be any longer than standard.
The commodore Gabriels are the right length to use every bit of added length permitted by 50mm bumpstop spacing. Those konis, and OME fronts are designed to work with no bumpstop spacing.
Steve.
michaelpiranha2000 wrote: The rear is in great condition. but has a broken crown wheel and pinon
I'll ring Climax today and see if I can get the compressed and extended length just in case. Reviews such as the one below don't really inspire to install Gabriels...
I initially tried the commo/hiace setups which were apparently the ducks nuts from info on here. May have well welded them solid! Dam they were insanely hard! They are cheap and can provide some extra travel if you get the correct lengths but that’s about it.
The Koni’s really made a world of difference, especially on the road. Being my daily, that does a lot of k’s, I needed something that rode better than a shopping cart.
We'll see, there could be something in the Koni range that is the correct length and at $380 a pair I think it's a reasonable extra expense.
Mal Leslie has a shock dyno and rebuilds and revalves Koni. He can dyno an existing shock (like an OME front) and then valve a Koni of the correct length to work in your application. He Dynoed some ranchos for me around '00 and I'd sort of forgotten about him, but he came up in a conversation yesterday.
It's still worth bearing in mind this though:
If you continue to use front OME springs, there is only maybe 20mm more travel available in the spring than the OME shock can accommodate. Spending Koni money (or worse, Koni money plus a revalving and dyno charge, as well as sourcing a shock to dyno) on a car that drives pretty good with no shocks in it to gain maybe 20mm of travel seems like a pretty big investment. Most people aren't willing to invest as much in a pair of shocks as they have in the rest of their suspension.
Personally, I'd run OME or Gabriel. If you later convert to RUF, where there is about an extra 100mm of travel to be gained, then by all means step up to a Koni, which you can then get valved to ride properly. Koni's are fantastic shocks, but you are doing more the screw up the way the front suspension works with a 50mm bumpstop spacer than any shock can help to fix.
Steve.
michaelpiranha2000 wrote: The rear is in great condition. but has a broken crown wheel and pinon
Because I'm in my shed today, I've had the chance to measure some shocks.
A Stock sierra front shock has 155mm of travel and a collapsed length of 265mm, extended length 425mm
An OME sierra front shock has 160mm of travel and a collapsed length of 280mm, extended length 435mm
So an OME shock uses up some "safety margin" in compression to allow 10mm more droop than standard. Interestingly, the shock isn't actually as efficient at packaging - note that it's 15mm longer compressed to net 10mm more travel. That's indicating the internal valving is much bulkier. Not surprising for an aftermarket shock that's designed to be more durable.
A stock vitara rear shock has 170mm of travel and a collapsed length of 305mm, extended length 485mm
From that, with some lower mount bushing changes, it looks like you could purchase a vitara rear shock absorber to suit. (both shocks are pin top eye bottom) or even try some stock vitara rear shocks. I have a pair of reasonable KYB vitara rears here you could try for nothing. They came off a wreck but they look to be in reasonable condition. Valving feels stiffer than a stock sierra leaf front shock but softer than a sierra OME front.
Another option would be to try 5125 bilsteins. They offer 175mm of travel and there is soft valving available. You'd have to import these from the states though. Our normal source for Bilsteins, Lowrange off road, doesn't offer the 7" travel shock in soft valving, but I'm sure they are available. The part number for the stiff valving is BE5-6252-H5. I think you'd want the softest possible valving which is 175/60. These are less efficient in travel again though as they are a monotube shock, so they are 470mm extended.
Steve.
michaelpiranha2000 wrote: The rear is in great condition. but has a broken crown wheel and pinon
I threw out my Gabriels as they were toast but I have no reason to doubt the measurements you've posted before for their length. It's reconfirmed something always thought was the case but I'd heard it dismissed as an issue so many times I'd forgotten about it. The commodore shocks are 100mm longer than a stock sierra shock, and 80mm longer than an OME shock compressed. That makes them too long to use with 50mm bumpstop spacing. Mine bottomed before I could fully compress my bumpstop.
This is bad for the shock, bad for the mounts, and bad for ride quality.
From my measurements, I'd be looking at vitara rear. I wouldn't recommend using an aftermarket rear shock designed for a vitara, as it will be far too stiff. A stock or stock replacement (like my KYB's) should be ok as a starting point.
Steve.
michaelpiranha2000 wrote: The rear is in great condition. but has a broken crown wheel and pinon
