Ride Quality---shock comparison

[Jameel]

My car: 1983 911 coupe, lowered to Euro, no bump steer spacers, recently aligned, new Boge shocks on rear this spring, presumed original Boge fronts. Michelin Pilot Sport AS3 new this spring. Fuchs 6 & 7. 122k miles.

My brother's car: 1979 911 coupe, stock US ride height, recently aligned, presumed orginal Bilsteins front and rear, Michelin Pilot Sport AS3 new this spring. Fuchs 6 & 7. 95k miles.

So when driving around rough city streets or highways with pronounced expansion joints, my car exhibits more of a sharp "bang-bang" and I can feel it in the seat. It gets pretty annoying. On faster back roads when I hit a bumpy corner at speed, it feels a bit like the car is wanting to skitter a little instead of staying grounded. Hard to be certain, but the car's ride didn't really improve after fitting the new rear shocks this spring.

When I drive my brother's car on the same streets, it takes the sharp bumps much better. There's much less sharp feel through the car's chassis and seats, and more of a "thoomp-thoomp" sound that a more newish car might exhibit. Yet, his car handles really well, it's not like its soft or mushy, it just feels like the shocks are doing their job better. It feels more sorted. It does have a bit more body roll being at stock US height, but that's the only knock against the car's handling.

I've read a bit here about Boge vs. Bilsteins, but didn't find an answer that would explain this situation. If someone has experience with both brands, does my explanation sound like a good comparison between the two brands? Could worn suspension bushings in my car also cause more of the "bang bang" over bad surfaces?

I'm planning to drop my front suspension and rebuild this winter, and want to pick the best setup for this car. Even if that means swapping out my new rear Boge shocks for Bilsteins.

[Trackrash]

Originally Posted by Jameel

Could worn suspension bushings in my car also cause more of the "bang bang" over bad surfaces?

I'm planning to drop my front suspension and rebuild this winter, and want to pick the best setup for this car. Even if that means swapping out my new rear Boge shocks for Bilsteins.

Yes, worn bushings can cause a harsh ride. Look at your rear torsion arms where they go through their covers. Evenly spaced? Evidence of metal to metal? New bushings made noticeable difference on my car.

Are your Boge shocks high pressure shocks like the Bilsteins? If not that could make a difference as well.

How do your sway bars compare?

[Jameel]

Originally Posted by Trackrash

Yes, worn bushings can cause a harsh ride. Look at your rear torsion arms where they go through their covers. Evenly spaced? Evidence of metal to metal? New bushings made noticeable difference on my car.

Are your Boge shocks high pressure shocks like the Bilsteins? If not that could make a difference as well.

How do your sway bars compare?

I don't know how the t-bars look out back. I'll check. I won't be surprised if they are shot though. Putting new shocks 5k ago didn't seem to have any effect on the ride. I don't know if they are high pressure. I just ordered new stock ones from EBS as a sort of "while you're in there" while my engine was out. I'll measure up the sway bars too. I haven't compared their sizes. I just remembered that I did put new sway bar links and bushings in the back of my car when I did the shocks.

[Jeff NJ]

If your suspension rubber is original, it is probably time to replace. I did this to my 88 a couple years ago and it definitely improved the sharpness and the ride.

Basically, if it was rubber and part of the suspension, I replaced it. Almost all of it was stock or near stock performance. I didn't go monoball, and kept it all rubber as this is not a track car and I didn't want too harsh a ride.

Sway bar bushings, spring plate bushings, front and rear control arm bushings (went with elephant racing on these), strut mounts, ball joints, tie rod ends were all replaced. It was all original and much of it was obviously not in great shape. I also had my Bilsteins rebuilt by Bilstein.

This also removed a slight shimmy at 80+, so something was definitely worn.

I lowered my car to probably a hair below Euro height and the bump steer kit definitely helped. You want the tie rods to be on the same plane as they were when it was at stock height. It does make a difference in the feel of the way it handles when it hits those bumps.

Obviously a good alignment and maybe a corner balance after that is required.

[Flojo]

Originally Posted by Jameel

My car: 1983 911 coupe, lowered to Euro, no bump steer spacers, recently aligned, new Boge shocks on rear this spring, presumed original Boge fronts. Michelin Pilot Sport AS3 new this spring. Fuchs 6 & 7. 122k miles.

..

So when driving around rough city streets or highways with pronounced expansion joints, my car exhibits more of a sharp "bang-bang" and I can feel it in the seat. It gets pretty annoying. On faster back roads when I hit a bumpy corner at speed, it feels a bit like the car is wanting to skitter a little instead of staying grounded. Hard to be certain, but the car's ride didn't really improve after fitting the new rear shocks this spring.

comparing one's own car to an other is allways very difficult, as partially new parts can provide a different handling to the other car, as one doesn't know how the old parts actually perform, what their wear status is.

and "asuming" that not recently changed parts are still good, is not really a good basis to start with.

looking at the 911's drive chassi you have:
- bushings
- shocks
- torsion bars
- sway bars

further: worn engine/tranny mounts can effect handling too if the engine swabbles aroung when cornering

unless you are not absolutely sure about ALL of these part beeing in good order it may be the day to adress them when you are not happy about your cars handling

and since there are "hidden" parts you cannot check from the outside, such as the torsion bars or the front shocks in the tube..., well, you must decide to retreive them to check.

and even if the bushings look ok (not torn/ripped) they get worn, get hard and crunch making any alignment actally a bit obsolete.

so don't "asume", but rather "make sure".

[Bill Verburg]

Originally Posted by Jameel

My car: 1983 911 coupe, lowered to Euro, no bump steer spacers, recently aligned, new Boge shocks on rear this spring, presumed original Boge fronts. Michelin Pilot Sport AS3 new this spring. Fuchs 6 & 7. 122k miles.

My brother's car: 1979 911 coupe, stock US ride height, recently aligned, presumed orginal Bilsteins front and rear, Michelin Pilot Sport AS3 new this spring. Fuchs 6 & 7. 95k miles.

So when driving around rough city streets or highways with pronounced expansion joints, my car exhibits more of a sharp "bang-bang" and I can feel it in the seat. It gets pretty annoying. On faster back roads when I hit a bumpy corner at speed, it feels a bit like the car is wanting to skitter a little instead of staying grounded. Hard to be certain, but the car's ride didn't really improve after fitting the new rear shocks this spring.

When I drive my brother's car on the same streets, it takes the sharp bumps much better. There's much less sharp feel through the car's chassis and seats, and more of a "thoomp-thoomp" sound that a more newish car might exhibit. Yet, his car handles really well, it's not like its soft or mushy, it just feels like the shocks are doing their job better. It feels more sorted. It does have a bit more body roll being at stock US height, but that's the only knock against the car's handling.

I've read a bit here about Boge vs. Bilsteins, but didn't find an answer that would explain this situation. If someone has experience with both brands, does my explanation sound like a good comparison between the two brands? Could worn suspension bushings in my car also cause more of the "bang bang" over bad surfaces?

I'm planning to drop my front suspension and rebuild this winter, and want to pick the best setup for this car. Even if that means swapping out my new rear Boge shocks for Bilsteins.

There may be other factors as well but Bilstein will ride and handle better than Boge, the Bilsteins aren't perfect though, they still use the antiquated valving developed back in the '60's and 70's. Have them revalved w/ a custom digressive valve set and there is another whole level of improvement waiting for you.

[Driven97]

Originally Posted by Jameel

My car: 1983 911 coupe, lowered to Euro,

My brother's car: 1979 911 coupe, stock US ride height,

This throws a flag for me. 1983 ride heights were the same for the world. Monster truck height was 75-82 US only.

Any photos of this US height and Euro height? I'm guessing your car is much lower than factory euro height.

[tirwin]

Lowering a 911 without any other adjustments reduces the suspension travel distance. It could be that what you're feeling is the suspension maxing out. I have a friend that has this problem on his '83 right now. We went for a ride the other day and you can feel and hear it. He is in need of a suspension refresh and we're talking through options and budget now.

As Bill mentioned, a custom digressive valve job does wonders. How much resistance the strut provides is a function of strut compression speed and force. With a normal strut the response curve is linear. With a digressive valve the response is non-linear. The goal is to get comfort when you want it and stiffness when you need it. Low force and compression velocity and the suspension is relatively soft. High force and compression velocity and it gets really stiff. It can be a beautiful thing.

[Driven97]

Originally Posted by tirwin

Low force and compression velocity and the suspension is relatively soft. High force and compression velocity and it gets really stiff. It can be a beautiful thing.

I'm being pedantic, but that's backwards. Digressive shocks ramp up forces very quickly at low shaft speeds for good body control in transitions, then taper the gain off at high shaft velocities for bumps.

[Tippy]

Don't forget wheel size and tire sidewall height makes a big difference.

[Jameel]

Originally Posted by Driven97

This throws a flag for me. 1983 ride heights were the same for the world. Monster truck height was 75-82 US only.

Any photos of this US height and Euro height? I'm guessing your car is much lower than factory euro height.

My goof. I of course know my '83 came at "Euro" height from the factory. It has not been lowered to my knowledge. Measurements at the fender (I know, not the best metric) are Euro +/- a scosh.

Originally Posted by tirwin

Lowering a 911 without any other adjustments reduces the suspension travel distance. It could be that what you're feeling is the suspension maxing out. I have a friend that has this problem on his '83 right now. We went for a ride the other day and you can feel and hear it. He is in need of a suspension refresh and we're talking through options and budget now.

As Bill mentioned, a custom digressive valve job does wonders. How much resistance the strut provides is a function of strut compression speed and force. With a normal strut the response curve is linear. With a digressive valve the response is non-linear. The goal is to get comfort when you want it and stiffness when you need it. Low force and compression velocity and the suspension is relatively soft. High force and compression velocity and it gets really stiff. It can be a beautiful thing.

Great info Tim. I don't think its bottoming on my car though. It's harsh, but not that harsh. I should also add that last year I was running the car at high tire psi because I was a complete idiot back then and didn't know any better. Like 45psi all around. I thought it was harsh then. And it was. Then I read the label in the engine bay about proper levels and let a bunch of air out. HUGE difference. I got "thoomp thoomp". But now it's almost like the tires are over inflated again. Weird.

Originally Posted by Tippy

Don't forget wheel size and tire sidewall height makes a big difference.

That's why I think my brother's car is a good comparison. We're running identical wheels and tires.

I have another thread going about a goose stuck in my front fender (front suspension squeaks) so I've already planned to drop the front this winter and refresh the suspension. Looks like I might as well do the back too. It would be stupid to do just one half of the car. I rebuild my engine last winter, start to finish, in four months. I can't imagine f+r suspension would take longer, or am I dreaming. I've got to get this baby singing so I can drive it to Rennsport next year!!

[Driven97]

If you haven't had it apart before, you'll laugh at how simple the suspension is on these cars. Cakewalk.

[Jameel]

Originally Posted by Driven97

If you haven't had it apart before, you'll laugh at how simple the suspension is on these cars. Cakewalk.

After doing a complete rebuild of my 3.0 last winter, you don't know how comforting those words are.

[Trackrash]

Originally Posted by Driven97

I'm being pedantic, but that's backwards. Digressive shocks ramp up forces very quickly at low shaft speeds for good body control in transitions, then taper the gain off at high shaft velocities for bumps.

How does this compare to Konis? I always felt my Konis were stiff on small imputs, but moved easy on large bumps like dips.

[Trackrash]

Originally Posted by Trackrash

Yes, worn bushings can cause a harsh ride. Look at your rear torsion arms where they go through their covers. Evenly spaced? Evidence of metal to metal? New bushings made noticeable difference on my car.

Are your Boge shocks high pressure shocks like the Bilsteins? If not that could make a difference as well.

How do your sway bars compare?

I was under the impression that Boge started using gas pressure shocks similar to Bilsteins at some point? Were your new shocks hard to compress when you installed them?

My comment on sways was in reference to the size of your sway bars. If they are larger that could be a source of extra harshness.

[Jameel]

Originally Posted by Trackrash

I was under the impression that Boge started using gas pressure shocks similar to Bilsteins at some point? Were your new shocks hard to compress when you installed them?

My comment on sways was in reference to the size of your sway bars. If they are larger that could be a source of extra harshness.

Im pretty sure I remember them being rather easy to compress actually.

I'll measure both sways.

I just talked to Shannon at Elephant racing and he said the Boge shocks are inferior quality and feel to the Bilsteins all around. I guess I can put Bilstein inserts up front in the Boge spindles. So that's good news.

[gregwils]

My car came with Boge in the front, which I replaced with Bilstein Heavy Duty inserts. I also installed Bilstein HD in the back. I replaced every rubber suspension bushing with ERP rubber components - every rubber component ERP makes is on my car. My car is at euro ride height (25.5/25 IIRC). Bump kit is installed. I used the DIY triangulation method to corner balance. Pretty new Michelin Pilot Sports.

I find the ride on my car to be very compliant - even surprisingly compliant, but it still feels nicely planted in all street driving.

[faverymi]

Originally Posted by Bill Verburg

There may be other factors as well but Bilstein will ride and handle better than Boge, the Bilsteins aren't perfect though, they still use the antiquated valving developed back in the '60's and 70's. Have them revalved w/ a custom digressive valve set and there is another whole level of improvement waiting for you.

Bill:

Can you share who provides this service?

Thanks

[Driven97]

Originally Posted by Trackrash

How does this compare to Konis? I always felt my Konis were stiff on small imputs, but moved easy on large bumps like dips.

I'm no expert, and actually have no clue if the 911 specific Koni Sports are any different, but typically they don't have much compression damping at all. However you can dial up quite a bit of rebound. On my "other" car I was able to compress brand new sports by hand even set at full stiff.

Here's a dyno plot of a Koni Sport for a Toyota MR2 I found using Google:


The top is compression, bottom is rebound.

FYI, "large bumps like dips" is actually probably in the low speed range. High speed is sharper impacts like a section of pavement higher than the previous one, or in the rebound direction a gap in the pavement.

[Driven97]

Originally Posted by faverymi

Bill:

Can you share who provides this service?

Thanks

Bilstein themselves, Elephant, Performance Shock Inc, should all be able to do 911 Bilsteins. Maybe FatCat can if they have the right tool for the front insert.

You aren't going to be able to talk to anyone at Bilstein. Just fill out your paper and send them in.

Chuck @ Elephant is the go-to, he was easy to get a hold of. Only negative for me is that he was unwilling to deviate from his canned valving for my requests. He'd do a great job for 99.5% of Pelicans.

PSI has been a little tough to get a hold of for me, but I'd be willing to give them a try if I had to do it again.

FatCat would be a last resort only for me, ymmv.

Relevant needed info would be sprung corner weight, effective spring rate, and motion ratio. Another reason to use Elephant, you just tell them your torsion bar size and your car year / mods.