Noob needs help with suspension

[Mr. Radar 2]

Hi everyone,

I recently bought the Audi Quattro TT-02 and naturally wanted more ground clearance. So I modified the chassis as suggested by Mark Bryan on YT. Right now clearance is a bit over 20 mm which is enough for the moment since I do not want to touch drive shafts and cups. However, bottoming out the super mini CVA shocks now leaves a 5 mm air gap below the chassis. I'm fairly new to RC cars but understood that the chassis should bottom out before the shocks. Presumeably to not overstrain the shock mounts? Anyway, I do not intend to hit large jumps with this car but will this be a problem in the long run?
What are my options? Either increase leverage ratio via the lower suspension arm which I do not think is possible or find a shock with the same length (~59 mm) and longer stroke?

Thanks

Karsten

[Pylon80 4316]

Hi Karsten,

I don't think you should aim to make the lower deck of any car bottom on the ground. Using the shocks to limit suspension travel is fine unless the piston rod start hitting the shock bladders as they could puncture them. But that would only happens if you did a lot of hard jumping which you probably shouldn't be doing with a TT-02 It would also be possible to use some o-rings on the outside of the shock to provide a softer travel limiter if you really wanted.

I have mine set to 13mm ride height and 19mm of droop (droop is how high you have to lift the car before the wheels leave the ground). That ratio of ride height vs droop is critical for good handling. Jacking up a TT-02 to 20mm with hardly any droop left will not produce very good handling I'm afraid.

There are other things limiting the suspension on that car such as universals/drive axles, limiting tabs on the uprights etc as you probably already noticed.

The TT-02 is a very capable rally car but it requires a lot of fiddling and modifications to get there. One thing that is a problem though is the very soft plastic used on the lower arms which make the shock come loose when driving off-road, where the car is subjected to a lot of vibrations. I do not really have a good fix for that yet other than re-tightening screws every 15min!

Best of luck and let us know how it goes!

[Kowalski86 5024]

I'm not sure if Mark Bryan mentions it, you should pick up some metal low friction suspension balls for any rallying. The plastic ones wear quickly as they get dirty, and can pop out in a bog hit.

Metal axles/universals will give you more range for a higher ground clearance (you can run a set of long shock eyelets and mount them in their upper spot) but you'll sacrifice handling in the process.

 

[Mr. Radar 2]

36 minutes ago, Pylon80 said:

Hi Karsten,

I don't think you should aim to make the lower deck of any car bottom on the ground. Using the shocks to limit suspension travel is fine unless the piston rod start hitting the shock bladders as they could puncture them. But that would only happens if you did a lot of hard jumping which you probably shouldn't be doing with a TT-02 It would also be possible to use some o-rings on the outside of the shock to provide a softer travel limiter if you really wanted.

I have mine set to 13mm ride height and 19mm of droop (droop is how high you have to lift the car before the wheels leave the ground). That ratio of ride height vs droop is critical for good handling. Jacking up a TT-02 to 20mm with hardly any droop left will not produce very good handling I'm afraid.

There are other things limiting the suspension on that car such as universals/drive axles, limiting tabs on the uprights etc as you probably already noticed.

The TT-02 is a very capable rally car but it requires a lot of fiddling and modifications to get there. One thing that is a problem though is the very soft plastic used on the lower arms which make the shock come loose when driving off-road, where the car is subjected to a lot of vibrations. I do not really have a good fix for that yet other than re-tightening screws every 15min!

Best of luck and let us know how it goes!

Yes, I noticed that I reached the limit of range of motion of the suspension. Going further definitly does not make sense.

Maybe to clarify, the 20 mm ride hight is in the settled state. Fully extended droop is 25 mm. But maybe I should lower it a little more. You are running ~32% of sag while I am sitting at 20%. Might be on the harsh side. On my mountainbike I run 25 to 30 depending on trail...if these two worlds are even remotely comparable...

I built the shocks using the pistons with one hole. Would you consider this overdamped for this car?

I noticed the soft plastic on the lower arms. There is practically no indication of when you start to strip the threading. Curious choice of material for this critical piece of the suspension.
Will try it out once weather improves.

 

5 minutes ago, Kowalski86 said:

I'm not sure if Mark Bryan mentions it, you should pick up some metal low friction suspension balls for any rallying. The plastic ones wear quickly as they get dirty, and can pop out in a bog hit.

Metal axles/universals will give you more range for a higher ground clearance (you can run a set of long shock eyelets and mount them in their upper spot) but you'll sacrifice handling in the process.

 

I do not remember him mentioning these but thanks for the heads-up. Will replace them once the plastic ones fail.
I actuall fitted the long eyelets on the shocks and mounted them in the upper position.
Well, let's see how it goes.

Thanks for your replies!

[Kowalski86 5024]

41 minutes ago, Mr. Radar said:

I do not remember him mentioning these but thanks for the heads-up. Will replace them once the plastic ones fail.
I actuall fitted the long eyelets on the shocks and mounted them in the upper position.
Well, let's see how it goes.

Thanks for your replies!

One piston hole is perfectly fine for a TT02, 2 holes are okay if soft, three holes can get bouncy.

The ball cups don't necessarily "fail", they just wear out a bit quickly, and can wear your suspension arm. It's an area where Tamiya really should have used aluminum from the get go (they can't cost much to make).

If you have the stock axles/drive cups, you won't have full suspension travel with long eyelets and the upper position.

[Mr. Radar 2]

We'll I guess I need to try once weather improves. Thanks for your input.

[Mr. Radar 2]

On 2/5/2024 at 11:06 PM, Pylon80 said:

Best of luck and let us know how it goes!

Had the chance to go for a spin. It reacts really lively to steering input. Definitely need more practice while also reducing max power output of the motor. The dust cover does a great job at keeping dirt out it also keeps the heat in. I might add a few venting holes above the motor. And go for smaller batteries to limit driving time.
The ground was a little tricky as well. Hard-pack with gravel on top.

I also took my Kyosho Beetle out and that one turns like a bus compared to the TT-02. Or rather, it doesn't turn at all under the slightest bit of power.

All in all, great fun!

[Otis311 423]

I was wondering what springs are being used to obtain 30% droop. I have tried a variety of springs in my collection and I can only barely get the suspension to sag under it's own weight. This is for a TT-02 in rally setup (suspension modded as descried in OP) using super mini CVA with no spacers. Thanks!

[ThunderDragonCy 9114]

Tamiya 53163 spring set is the road/rally set but even that won't get you lots of sag, but more than kit springs. I run these on my fwd rally with 55mm stroke shocks. I have mini shocks (64mm) with short eyelets on my rwd rally car (admittedly not a TT02) so i can use buggy front springs that are much softer. 

[Otis311 423]

4 hours ago, ThunderDragonCy said:

Tamiya 53163 spring set is the road/rally set but even that won't get you lots of sag, but more than kit springs. I run these on my fwd rally with 55mm stroke shocks. I have mini shocks (64mm) with short eyelets on my rwd rally car (admittedly not a TT02) so i can use buggy front springs that are much softer. 

Front buggy springs on longer shocks would definitely be better. I see why long damper spec rally vehicles are sought after now. The 53163 spring set was on my radar. I have that for some other cars. I don't like buying the expensive sets of springs when I really only want the soft red springs, but this is the hobby I chose.

Are there any good yet inexpensive aftermarket springs for the CVA shocks?

[Pylon80 4316]

1 hour ago, Otis311 said:

Front buggy springs on longer shocks would definitely be better. I see why long damper spec rally vehicles are sought after now. The 53163 spring set was on my radar. I have that for some other cars. I don't like buying the expensive sets of springs when I really only want the soft red springs, but this is the hobby I chose.

Are there any good yet inexpensive aftermarket springs for the CVA shocks?

I use the 53163 set on a TT-02 rally car. These springs came out back when some cars were designed with almost vertical shocks like the TL-01. On a TT-02 the shocks are much more reclined and as a result the effective rate as felt at the wheel is very soft. And so I only use the blue at the front and yellow at the rear. The reds are too soft in my experience for a TT-02. If you try them you will see how the car squats to the point of scaping the rear on acceleration, and with the kit motor!

There are no aftermarket soft springs as far as I know with even the "very soft' ones often being too hard (yeah racing).

For a TT-02 rally if you can't find the 53163 set the best springs are simply the black ones included in the TT-02 super mini CVA set. These are shorter than in the 53163 set but very soft. I think, between blue and yellow although I would have to remove them and check to be sure.

[Otis311 423]

Thank both @ThunderDragonCy and @Pylon80 . I appreciate you input. I will try some of your recommendations.

[StueyS 52]

If you want more up travel to go with the extra droop, you probably need taller shock towers so you can have longer stroke shocks. This is not so easy on a TT02, I have a Type S built as a Rally car which has shock towers that can be replaced and modded to raise the upper mounting point. Having the chassis capable of bottoming out before the shock travel ends is desirable IMO, my race buggies can do this and it takes the strain off of the shocks.

[Otis311 423]

38 minutes ago, StueyS said:

If you want more up travel to go with the extra droop, you probably need taller shock towers so you can have longer stroke shocks. This is not so easy on a TT02, I have a Type S built as a Rally car which has shock towers that can be replaced and modded to raise the upper mounting point. Having the chassis capable of bottoming out before the shock travel ends is desirable IMO, my race buggies can do this and it takes the strain off of the shocks.

I have been thinking of ways to raise the upper shock mounting point. I looks like Hop-up # 54947 Carbon Damper Stay II has higher mounts for a ~61mm shock. I could use something like that with CVA minis and soft buggy springs. This was supposed to be a cheap build lol.