KTM RC 390 Suspension Geometry Settings

[tt2013]

Hi All,

I have a KTM RC 390 with Andreani fork cartridge kit in the front and Ohlins KT-303 rear shock. The Ohlins rear shock has an adjustable ride height.

Last Saturday, my friend, who races 300cc motorcycles, told me that my motorcycle steers very heavy. He mentioned raising the forks by 5mm and doing the same with the rear. He also mentioned that I seek advice from other people racing a KTM RC 390 to ask them about their geometry settings.

Has anyone changed the geometry of their bike? If so, can you tell me what you did and how did it affect its handling.

 

[green_bread]

Ive heard that it is common to raise the front end by 3-5mm. I also know that I have a JRi shock with a stock front end, for now, and without raising the rear, the bike does steer VERY heavy.

The one thing Im not sure of is if you raise the front and the rear, both, if that will make the bike less heavy... if that makes sense. You arent really raising the rear in relation to the front if you are raising both, I guess.

 

[Major]

Adjusting the geometry by each end does different things. Tire profile has a very important impact on a bike's geometry. Taking advice from someone else is a good starting point, but you really need adjust the bike to your riding style and how the bike feels to you. If you are having a difficulty getting the bike to turn at entry you the adjust the front geometry by pulling the fork tubes through the triples in small increments (lowering the front end). If you are having a difficult time getting the bike to finish a corner you would raise the rear in small increments. These are very general rules and it can get a whole lot more complicated with many other variables to be considered.

 

[Old3]

Check your tire pressure and then test and tune, test and tune every variable, every adjustment, pressure, ride height, sag, rebound and compression until you get a feel for what they do and what you want.

 

[Ash797]

I am running the same andreani/ohlins suspension that you have and I'm a club racer in TX.

I have raised the front of the bike all the way up to where the fork tube is flush with the top triple. The fork caps are not being bound by the tension of the triple tree. I did this to put LESS weight on the front of the bike because, when I had 10 or 15mm(tried both) showing of the fork tube ABOVE the top triple, I didn't like how the bike felt while cornering. I did not change my rear ride height yet, from how it was sent to me as I have yet to have my sag properly set up.

In the end it's all about personal preference. Having your suspension set up will get you close but you'll still have to fine tune it your individual riding style.

 

[motoputz]

I just put mine back together with the Andreani fork cartridge kit and a K-Tech shock. The suspension shop that put the fork kit in and got me the shock recommended putting the forks in flush with the top of the triple clamp. Front sag should start at 30mm and rear sag should be 40mm. From their experience the bike corners better with a lower rear. I have only ridden the bike twice since I bolted everything back together and none of that riding was done on a twisty road at a fast pace. So I have not determined the best set up yet. But I can say that the new components and settings have improved corner turn in.

 

[Rexbo]

There's a lot of interaction between the front forks, rear shock, tires and riding style that contributes to how the bike responds to individual riders input, and everyone will have slightly different settings that work.

I have your exact same setup right now (but 160 lb weight), and here's what I've found to work so far, as a baseline:
- 110/70-17 Pirelli Supercorsa SC1 @28 psi on the warmers (adjust later for ambient temps coming off track)
- 25mm sag front
- Fork tubes flush with triple tree
- 2.25 turns CCW (out) from stop compression
- 2 turns CCW (out) from stop rebound (needs a little more tuning)

- 140/60-17 Pirelli Diablo Rosso 2 @26psi on the warmers (adjust later for ambient temps coming off track)
- 25mm sag rear
- 305mm eye to eye length on rear shock (thinking of going to 310mm)
- No comp/rbnd settings yet, needs work (at 2.5 turns CCW (out) on both)

Right now I still feel that the bike tends to run wide on corner exit and has difficulty holding a tight line, but the front feel is excellent so the next time I go out will be focused on adjusting the rear settings. Looking at the tires both front and rear I have a bit more to go on adjusting rebound

 

[ULW]

There's a lot of interaction between the front forks, rear shock, tires and riding style that contributes to how the bike responds to individual riders input, and everyone will have slightly different settings that work.

I have your exact same setup right now (but 160 lb weight), and here's what I've found to work so far, as a baseline:
- 110/70-17 Pirelli Supercorsa SC1 @28 psi on the warmers (adjust later for ambient temps coming off track)
- 25mm sag front
- Fork tubes flush with triple tree
- 2.25 turns CCW (out) from stop compression
- 2 turns CCW (out) from stop rebound (needs a little more tuning)

- 140/60-17 Pirelli Diablo Rosso 2 @26psi on the warmers (adjust later for ambient temps coming off track)
- 25mm sag rear
- 305mm eye to eye length on rear shock (thinking of going to 310mm)
- No comp/rbnd settings yet, needs work (at 2.5 turns CCW (out) on both)

Right now I still feel that the bike tends to run wide on corner exit and has difficulty holding a tight line, but the front feel is excellent so the next time I go out will be focused on adjusting the rear settings. Looking at the tires both front and rear I have a bit more to go on adjusting rebound

Not a KTM expert here, but try going lower in the rear to increase trail, which may help with the running wide issue. The Ducati 898-1098-1198 has the same issues running wide, and increasing trail through raising front, lowering rear, or taller front tire... actually the best way is to reduce the offset at the triples, but not always practical. Cures the holding a tight line issue you describe. Just another data point to consider.

 

[ratlab]

i'm running rear shock + 10mm with forks caps flush.i have andreani's and ohlins also..turns in well and holds a line,but does run a little wide at corner exit.i went up +10 because of the 150/60 doesn't want to finish the corner.i am running alpha 13's.this the only bike i have had that you can roll to the edge or over on the front tire and still have unused tire on the rear.i will probably go to 140/70 and play around between +5 and +8 on the shock.

 

[motoputz]

After 200 miles at Laguna Seca and having Dave Moss adjust preload and dampening settings at both ends I ended up with the forks raised 6mm above the top triple clamp (on Dave’s advice). I only road two sessions, about 30 or 40 miles, with the forks raised to that height and my corner entry was not that aggressive as I was riding around the lack of performance from the stock front brake. The bike handled better, turn in was sharp, I could move around mid-corner to pass with no drama and the rear stopped squirming around under acceleration out of turn 11. I will probably get to the track in August with better brakes and be able to fine tune the suspension settings.

 

[tt2013]

After 200 miles at Laguna Seca and having Dave Moss adjust preload and dampening settings at both ends I ended up with the forks raised 6mm above the top triple clamp (on Dave’s advice). I only road two sessions, about 30 or 40 miles, with the forks raised to that height and my corner entry was not that aggressive as I was riding around the lack of performance from the stock front brake. The bike handled better, turn in was sharp, I could move around mid-corner to pass with no drama and the rear stopped squirming around under acceleration out of turn 11. I will probably get to the track in August with better brakes and be able to fine tune the suspension settings.

Motoputz. Can you please tell me your suspension setup for the front and rear and what tires are you running. Did Dave Moss give you your sag number? I have seen videos from Dave Moss and he is a suspension expert and wish made more trips to Southern California.

 

[EdL]

After 200 miles at Laguna Seca and having Dave Moss adjust preload and dampening settings at both ends I ended up with the forks raised 6mm above the top triple clamp (on Dave’s advice). I only road two sessions, about 30 or 40 miles, with the forks raised to that height and my corner entry was not that aggressive as I was riding around the lack of performance from the stock front brake. The bike handled better, turn in was sharp, I could move around mid-corner to pass with no drama and the rear stopped squirming around under acceleration out of turn 11. I will probably get to the track in August with better brakes and be able to fine tune the suspension settings.

Motoputz, are you in bay area? Which shop installed your Andreani kit and how much did that cost you? Thanks.

tt2013, Dave goes to buttonwillow pretty often. Check out his calender. 2016 track calendar | Feel The Track

 

[motoputz]

This is what I have;

FORK

Preload all the way out

Rebound: All the way out

Compression: 3 turns out.

Total sag: 1 inch

K-Tech SHOCK

Compression: 7 Clicks out

Rebound: 8 Clicks out

Sag: 1.5 inches

It works for me now, there will be some more fine tuning next time I get it to the track. Dave was concerned that I was not getting full fork travel but it seems to be working..​

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[Mr Bean]

This is what I have;

FORK

Preload all the way out

Rebound: All the way out

Compression: 3 turns out.

Total sag: 1 inch

K-Tech SHOCK

Compression: 7 Clicks out

Rebound: 8 Clicks out

Sag: 1.5 inches

It works for me now, there will be some more fine tuning next time I get it to the track. Dave was concerned that I was not getting full fork travel but it seems to be working..
​

How much do you weigh?

Do you know your front and rear spring rates?

Have you added any ride height to the rear or is it set at stock length?

Which tyres do you use?

Does anyone know how much trail these bikes have?

 

[Rexbo]

Not a KTM expert here, but try going lower in the rear to increase trail, which may help with the running wide issue. The Ducati 898-1098-1198 has the same issues running wide, and increasing trail through raising front, lowering rear, or taller front tire... actually the best way is to reduce the offset at the triples, but not always practical. Cures the holding a tight line issue you describe. Just another data point to consider.

There's a couple of ways to skin this one... and I'm not sure which way to go on it yet. It's not quite apples to apples with the 898/1098 Ducatis since there are significant geometry differences between these bikes, not to mention ~150 hp.

For example my Ninja 250 race bike wanted the rear end of the bike as high as you could put it to handle well and have ground clearance. Since steering is not twitchy on the RC (its fairly heavy to me...) and I could use more ground clearance I'm going to try to raise the rear end first to see, and if it doesn't work, I'll let you all know.

 

[micahpearlman]

There's a couple of ways to skin this one... and I'm not sure which way to go on it yet. It's not quite apples to apples with the 898/1098 Ducatis since there are significant geometry differences between these bikes, not to mention ~150 hp.

For example my Ninja 250 race bike wanted the rear end of the bike as high as you could put it to handle well and have ground clearance. Since steering is not twitchy on the RC (its fairly heavy to me...) and I could use more ground clearance I'm going to try to raise the rear end first to see, and if it doesn't work, I'll let you all know.

I've gone the route of raising the rear and lowering the front. The only limitation I've hit is too much lift of the rear on hard braking and am slowly reversing. Talking to others racing the RC most seem to be going the opposite direction and raising the front and lowering the rear -- being limited to ground clearance. Those going for lowered rear and raised front seem to know what they are doing and are verifiably fast but for me it seems to be the exact opposite of what I'm feeling or needing from the bike.


Sent from my iPhone using Tapatalk

 

[motoputz]

170lb, I do not know the actual spring rates. The shop that did the work were suppose to size the spring to my weight. They might have got it spot on figuring that I have an inch of front sag with no pre-load. My recite shows the K-tech to have a 10.0 spring. I would take that to be 10Kg/mm of compression or maybe 10Kg/cm. not the best documentation from that group. No other suspension modifications. Using the stock Pirelli tires for now.

 

[green_bread]

For me, the best results came from raising the front end (lowering the forks in the clamps) and raising the rear end, both. Im sorry but I cannot provide measurements as they were provided by another member who has asked me not to share the info.

 

[Rexbo]

For me, the best results came from raising the front end (lowering the forks in the clamps) and raising the rear end, both. Im sorry but I cannot provide measurements as they were provided by another member who has asked me not to share the info.

Because, you know, nobody will figure it out and post it anyway

 

[green_bread]

Because, you know, nobody will figure it out and post it anyway

I'm very confident that they will and I hope they do. I also respect the request of someone who helped me out by not giving out numbers that they worked hard to find out on their own. I want this person to continue to help me in the future and they are an active member of this forum, so... It is what it is. I still offered helpful information.