Ohlins shocks for my GTM

[kabacj]

Although the Koni shocks that come with the kit are fine for street use I wanted to upgrade my shocks for track duty. During my motorcycle racing days I tried many shock companies. Penske and Ohlins were my favorites. But after riding on Ohlins shocks I put them on every bike. As a rider I had never seen a shock dyno graph but I can tell you it feels just like these graphs look. When you change one damping setting only that setting is changed and the changes are very linear. One click makes the same amount of change regardless of where you are travel of the adjustment. The other thing is that there is just so much adjustment. I could change spring rates and just add a few clicks to the dampers and I was good to go.

I did lots of research looking for somebody who understood these dampers and would be able to tune a set for the GTM. At SEMA I met the performance shock guys who built these dampers and they are very knowledgeable. The actual Ohlins designer from Sweden was in the booth answering questions.

A cool thing about these shocks is that you can upgrade them to 4 way adjustable by simply removing the adjusters and inserting a new valve. The other thing I like is the remote reservoir that you normally see piggy backed off the shock or attached with a stainless braided line is built in to the body. Nice and compact.



These shocks mount on the GTM without any modification to the frame because you can get different length end eyes. to position the shock body where you want it. I ended up putting bushings in the 1/2 inch holes of the frame so I could tighten up the tolerances between the end eyes and the frame. But thats just me looking for projects. Its not needed.

I thought you guys would be interested to see the dyno graphs that these shocks trace out. You can see how linear the adjustments are. Also note that this is three clicks per incremental trace change not just one. You can make very small changes in damping with one click.





the other traces are in my album. If you want to see them click on my ID and check out the other traces.

If anyone else has traces from shocks they put on the GTM I would love to see them. We can compare what folks have come up with as well as how each shock reacts to settings changes.

John

[carbon fiber]

hey john, sounds interesting. what kind of price range?

[crash]

Here's what I have for my project...

Ohlins tt44 Shocks.jpg

I think you made the right choice!!

[Fred Brewer]

John,,,
You've motivated me to finally send mine out to get dyno'ed. I be sending them out next week. I have a set of the old Yellows Koni's AND a set of the new Black Koni FSD's that I'm going to have done so we'll see how they compare to each other and of course to yours. I'll post up the plots once I get them back.

As a sidebar what spring rates are you planning to run and are you planning the same shock valving front to rear?

[kabacj]

Fred that's great news! It will be very useful to compare lots of dampers on the same dyno.

Carbon Fiber,

I don't know exactly what the shocks cost a piece as I have been working with Beau Kelly at performance shock since last April. We have been sending parts back and forth working out the clearances and then they worked their magic using the motion ratios and spring rates I got from Jim at Factory Five.
I called Beau and he is going to tell me what the setup would cost with the 1/2 inch end eyes so you can just pop them on the GTM and go. If you want you can always call him at 707 938 5664 x103.

Fred

The front and rear have different valving to account for the 450 front and 750 lb spring in the rear. I will start testing with the stock FFR spring rates. The performance shock guys feel that I will be able to run a softer spring on the track (the stock FFR springs) with the Ohlins damper as I can use the damper to control motion and the spring to support the weight of the car instead of using he spring to slow down the wheel in compression. Normally you run heavier springs on the track compared to a street setup. Bottom line is the damper controls the motion like it should and the springs only support the car.

Another cool thing is I have so much adjustment in the shocks as they are valved now I can go up or down 100 lbs with the spring rate easily without re valving and the same linear adjustability. My experience with other dampers is that you quickly run out of adjustment or the adjustment is less linear when you push the damping to the limit.

Crash I am sure that bucket of Ohlins dampers will clean up real nice. Change the end eyes revalve and you are good to go! Yet another selling point!! You can rebuild and revalve these dampers year after year.

Sorry to sound like a salesman, but I really like these shocks if you could not tell.

John

[kaloper]

John...Good work on the Ohlins. Do you know if there are any interference issues between the shocks and the upper a-arms and/or frame attach tabs. I, too am looking for an adjustable shock set-up for racing.

Also, would these Ohlins be installed spring down on the back or can they be inverted?

Thanks...Karl
GTM 362

[Roger Reid]

Also, would these Ohlins be installed spring down on the back or can they be inverted?

Thanks...Karl
GTM 362

The Ohlin's don't care what direction thay are mounted because they have a remote resevoir (air/oil seperation piston or bladder). Your limitation in the back is if the spring contacts the axle or cv boot.

[kabacj]

The Ohlin's don't care what direction thay are mounted because they have a remote resevoir (air/oil seperation piston or bladder). Your limitation in the back is if the spring contacts the axle or cv boot.

Roger is correct but I mounted both of my shocks right side up. You dont have the clearance issue in the rear like the koni shocks because the end eyes are longer . There is no interference with the frame either mounted right side up or upside down.

You can just move the shock over in the mount so it does not touch the boot.

Its easier to access the adjustment knobs with the shocks right side up. I have not mounted the rears as I am waiting to drop in the motor with the mendiola. I know i will have plenty of room however.

Here is a shot when I was doing mock up of the shocks without any axles of course.



Here is a shot of how the fronts mount.



John

[kabacj]

I mounted up my springs today. Before I inserted the springs I added these bearings which sit between the preaload nut and the spring. The nice thing is they allow you to really crank down on the preload without having the spring dig into the aluminum of the compressor nut. You can also see the preload adjuster tool to the right of the shock body. The pin on the handle fits into the adjuster ring.



Next I needed to compress the spring to mount it on the body. Sorta forgot that I needed to compress the spring to get lower spring landing on. I dont have a spring compressor and it would have taken me 45 min to get to my friends house to borrow his so I made one.



I ground some nice groves oh each of the fingers to mount on the spring coil and cranked down on it to compress the spring the needed 1.5 inches. Its a little light duty for the rear springs so i think ill just get a real compressor. But it worked 2x so junk laying around becomes a tool! I just love that.

And here is the finished product. Whats nice is there is just a little bit of preload so the springs with the adjuster backed off all the way. They don't rattle free when the shock is drooped all the way out.



John

[Roger Reid]

Looks like a nice clean build John. I like it.

[kaloper]

Thanks for the information and the pictures. I was worried that the adjusment knobs would interfere with the upper a-arms, however, it looks like there is plenty of room. Do you know the turn-around time in getting a set of these shocks made?

Thanks...Karl
GTM 362

[kabacj]

Once we had figured out all of the measurements took maybe 2 weeks to turn around the shocks.

If you want Performance shock can just copy my measurements and your quickly on your way. The only thing you need to decide is if you are going to go with the 1/2 inch mounting bolts or machine them up with new spacers like I did.

Performance shock can do it all for you if you do choose to go with the machined spacers and heavy duty end eye.

John

[kabacj]

In order to mount the springs on the Ohlins shocks the springs need to be compressed enough to put the retainer on the end.

Its an elegant solution as long as you have a way to compress the springs.

I forgot I needed a spring compressor on the day I was ready to mount the springs, however I was not going to let a little thing like not having the right tool stop me from assembling the shocks . I grabbed some threaded rod and some bar stock and made a spring compressor.


Well even with the 450 lb spring it was a little taxed. I am an adrenaline junkie, but this was one of those kids don't try this at home moments.


There was no way I was going to compress the 750 lb spring with that tool.

I did a search for how people mount their springs and there are lots of easy to fabricate ideas out there.

I liked the official Ohlins tool but I surely was not going to pay the hefty price tag.

I figured I could make that thing for 1/10th the price. How hard could it be? Famous last words.

Well turns out I don't have any of the right tools for this job, but I made due with what I had.

My woodworking router table, 36inch wood lathe, drill press and lots of hand work and this is what I came up with.
I needed to machine 2 thou off the rods and two thou off the sliders ID. Make the sliders press fit into the top plate. Cut the holes with circle cutting tools which are a single cutter on an adjustable beam. Took forever, but it worked well.






Its still not done yet as I need to remake the linkage on the cheap jack and mount the jack to the platform, but it works like a charm. I was able to change the spring in 30 seconds without any drama. It will be great for the track as I can quickly and effortlessly swaps springs while testing. I can also break down the tool and pack it away when not in use.

The materials cost me 70 bucks and I can do everything that the pro ohlins tool can do. Whoo hoo!

In the event I get longer or shorter shocks I can use the adjustment pins to quickly change the size of the tool.

If you do end up getting these shocks do an image search for compressor solutions and there are many options out there that are easy to make.

John

[crash]

Not that your new tool isn't cool, because it is, but why not just buy the proper length springs?

[kabacj]

Yep, sorry I did a bad job explaining why the tool was needed in the first place.

Here is a closeup of the spring retainer.



notice the shoulder that captures the retainer and the nice o-ring to prevent vibration.


When the spring is fully extended there is maybe 1/4 of an inch of pre load in my case because I put torrington bearings in between the tightening nut and the top of the spring.



With out those bearings there is only 1/8 of an inch of preload on the spring. Just enough so it never rattles free without any preload at full droop. Its kinda nice really. All the ohlins shocks I have dealt with have this same setup. Maybe other ohlins damper bodies are not setup this way. The ones you have from an open wheel car are not in the Ohlins catalog I get. However Ohlins sells and uses a tool like mine in order to install the correct 8 inch spring on the standard damper.

Here is what the retainer looks like when you compress the spring.



Could you get an inch shorter spring and not use the tool? Of course you could. You have less pre load of course. Could you make a longer threaded section on the body of the shock in order to mount like others do. Sure you could. Not sure why Ohlins makes the body this way, but they do.

Its fine with me. Any excuse to get another tool is justification in itself in my book.

John

[crash]

Interesting. Yes the lower spring seat is different on mine. It is a threaded collar that needs a spanner wrench just like the upper adjusting rings. Looks like you have plenty of room to run a 1" shorter spring and still have plenty of adjustment. I have just always been of the opinion that the spring should not be under a bunch of preload, but that there should also be room both above and below to make adjustments with the upper collars. If the springs are at either end of their adjustments with the collars, then it is probably time to adjust rates. Just my opinion though. Looks like it will work just fine the way you are using them, so long as the required preload isn't too much. It doesn't make for an easy change with the shocks in the car though.

[kabacj]

Good point about changing the springs on the car. Yeah no way that's happening.

Ohlins has a lift setup like the master lift folks have installed. It's used by some of the OEMs. The porsche lift setup you can get on the 911 was outsourced to ohlins.

I ll need shorter springs for that setup and they design the lift to fit on this body. So seems the engineers agree you can run a shorter spring and be fine.

I'd rather make the tool then use shorter springs to start anyway. I don't want my build to be over too soon.

What will i do with all the free time?

John

[flickery8]

Fred that's great news! It will be very useful to compare lots of dampers on the same dyno.

Carbon Fiber,

I don't know exactly what the shocks cost a piece as I have been working with Beau Kelly at performance shock since last April. We have been sending parts back and forth working out the clearances and then they worked their magic using the motion ratios and spring rates I got from Jim at Factory Five.
I called Beau and he is going to tell me what the setup would cost with the 1/2 inch end eyes so you can just pop them on the GTM and go. If you want you can always call him at 707 938 5664 x103.

Fred

The front and rear have different valving to account for the 450 front and 750 lb spring in the rear. I will start testing with the stock FFR spring rates. The performance shock guys feel that I will be able to run a softer spring on the track (the stock FFR springs) with the Ohlins damper as I can use the damper to control motion and the spring to support the weight of the car instead of using he spring to slow down the wheel in compression. Normally you run heavier springs on the track compared to a street setup. Bottom line is the damper controls the motion like it should and the springs only support the car.

Another cool thing is I have so much adjustment in the shocks as they are valved now I can go up or down 100 lbs with the spring rate easily without re valving and the same linear adjustability. My experience with other dampers is that you quickly run out of adjustment or the adjustment is less linear when you push the damping to the limit.

Crash I am sure that bucket of Ohlins dampers will clean up real nice. Change the end eyes revalve and you are good to go! Yet another selling point!! You can rebuild and revalve these dampers year after year.

Sorry to sound like a salesman, but I really like these shocks if you could not tell.

John

Would you go with the same springs and shocks today? The end of last year things were feeling very springy and bouncy for me.

[kabacj]

Would you go with the same springs and shocks today? The end of last year things were feeling very springy and bouncy for me.

100% absolutely yes.

As I have added aero to the car getting the shocks to work properly is even more difficult. Adding over 1,000 lbs of downforce significantly changes the spring rates and of course damping rates as well.

Since performance shock setup the rates and damping for me i have more grip than ever. The body is totally under control even pulling nearly 2 Gs. Even on the street the setup is not overly harsh. For street use sure it's stiffer then any production car with exception to those cars with "race or track" damping rate settings.

Ohlins does not sponsor anyone. Even top teams pay for their equipment. I figure that says something

I am friendly with guys who work for a shock manufacturer. They tell me Ohlins are in a league of their own. I believe it.

Can you get the same results with a high end Penske shock? Probably. I have used them as well, but in my experience they don't have the Ohlins Magic.

The other thing that is nice about the the Ohlins is the fact that you get the same benefits of a remote reservoir shock with the reservoir built in.



Ok commercial over. But hey you know I'm being honest because I didn't get anything for free.

John

[The Stig]

Hi John. This is great information, and well stated. I looked into using 3 way adjustable Penske shocks with remote reservoirs for my car, but I never got to the point that I was ready to pull the trigger and do it. This is the first time that I've seen anyone actually present a detailed analysis on the Ohlins shocks. I can see that if anyone were ready to move up to the top level of shocks and dampers, this might be the route to take.

Thanks for the info.

Quick question: For the novice, who might be a little hesitant to buy these, simply because of the complexity of dialing them in for your car, what would you estimate the learning curve to be as far as being comfortable with making educated (correct) adjustments that truly help you meet your goals for how the car handles?

Thanks,
Mike

[kabacj]

Quick question: For the novice, who might be a little hesitant to buy these, simply because of the complexity of dialing them in for your car, what would you estimate the learning curve to be as far as being comfortable with making educated (correct) adjustments that truly help you meet your goals for how the car handles?

Thanks,
Mike

Hey Mike

For general use an adjustable shock is pretty easy to figure out. First you need to get the spring rates where you want them. I think the stock GTM rates are a great sporty setup. You can track the car and drive it on the street both with good results.

Next find a good race shop. My shop's customers are flying lizard racing etc etc. Tier one road race teams. They will know how to match a shock to the wheel and spring rate of the GTM. A good shop will re valve the shock as many times as you want free of charge. Next you get yourself a set of adjustable shocks. A good race shop will already have the shocks setup for damping the spring and wheel rate you have so you set the adjustments in the middle and drive. Next you go full stiff amd full soft on each adjustment and see which one you like better. In the end you sneak up on the setup you like best.

As you go faster on the track you will typically need to change springs and damping to account for new loads.

So to answer your question. It's not hard as long as the shop you are working with is good. If you ask for a set of shocks and the shop does not send you a form to fill out with all of the engineering specs of the car, move on.

Hope that helps

John