Triumph Rat Motorcycle Forums banner
  • Hey everyone! Enter your ride HERE to be a part of this month's Bike of the Month Challenge!

1 - 7 of 7 Posts

·
Registered
Joined
·
147 Posts
Discussion Starter · #1 ·
I am trying to get my new-to-me '06 Thruxton set up right, but the problem is this is my first bike, so I have no comparisons, and I don't know what "right" is! I just changed the helibars our for stock, and love the look and feel, so my first "mod" was a success, even if it was just changing back to stock!!

My question is, what should the front shocks be set to for a rider of about 195lbs? I see the graduated lines on the indicator rod, but cannot find a table saying what the setting should be for rider weight.

Also, are there any adjustments that can be made to the rear shocks to stiffen them up, or are new springs the only way? Do you recommend that for someone my size?

Cheers!
 

·
Registered
Joined
·
1,893 Posts
So you weigh about what I do with my gear on. The Thrux is always going to be rather soft compared to the typical sport bike, but if you ride a buddy's sport bike you'll get a sense of what it should feel like.

The Thruxton has 120 mm of front suspension travel and 105 mm of rear travel. You want the sag with rider (static sag) to be about 30% of this. There are lots of good articles on the web on how to measure this. I happen to think this is the best.

http://www.sportrider.com/tech/motorcycle_suspension/index.html

The stock front spring has a spring constant of 0.72 kg/mm. To get the right sag at the front, you really need about 0.91 kg/mm, i.e. a stiffer spring. No amount of preload that you can dial in the front can stiffen the spring, it can only change the force at which the spring starts to further compress. So for example, if you dial the adjusters all the way in (about 2 cm, this means it will take 20*0.72 kg = 14.4 kg before the spring compresses. With a stiffer spring, you need less preload, which means the spring starts compression earlier, which gives you more control on the bumps and the suspension is more supple.

The rear shock is adjustable. You can get the right static sag, but it's compression and rebound damping is awful.

If you are just cruising around, then just stiffen up the front and rear and live with it as is. If you want more fun in the twisties, with less brake dive and harshness, then get a set of RaceTech 0.91 kg/mm springs, and Traxxion Dynamics damper rods with RaceTech Gold Emulators. That gives you rebound and compression damping control and adjustable preload. There are lots of good rear shocks. Its about $320 plus a few hours of your time.

For the rear, I use Ohlins, adjustable for preload only. Hagons and other shocks can give you adjustable compression and rebound damping too as can more expensive Ohlins.
 

·
Moderator
Joined
·
30,596 Posts
NorthernThrux has posted some great info for you there, but before you go too far, may I suggest that you just ride the bike as is for a while?

The only reason I say that is because this is your first bike - so it makes sense to get a bit of experience on it. The stock thrux may not be perfect, but I would say get 3000 miles on it, get the feel, ride some twisties, and then do the mod. You will almost certainly say "I wish I'd done this sooner", but only because you'll be able to tell the difference.

Right now, because you're new to it, having done the mod you may find that you're not sure how it should feel, just because of a lack of general riding under your belt.

I don't mean to be condescending here - I just think you will appreciate your mods more once you have a bit of riding experience.

But at the end of the day - it's your bike, do what feels right to you. The suspension upgrade is certainly a reasonable one - I will be doing shocks and forks on my bonnie pretty soon.

Cheers!
 

·
Registered
Joined
·
147 Posts
Discussion Starter · #4 ·
Good advice!

Thanks Gents - some good advice there.

I cannot afford to go and change the suspension out yet, so I am looking more for advice on what I can do to the current setup to make it best for what I need. Living in Houston, there are really no "twisties" that I know of, but I think that is the feel I am looking for, so from what I am hearing here, I will crank the preload as high as I can with the stock shocks and see how that feels, unless anyone can convince me otherwise!

Cheers!
 

·
Registered
Joined
·
1,893 Posts
Yeah, unless you have ridden a lot of other bikes, I'd totally agree. Ride for a while, get your sense of how the thing handles and then figure out what you want to do. Ride with the shocks on full preload and lowest preload, to get a sense of how these effect handling. Full preload might make you bounce off some bumps, because there isn't enough rebound in the mix. Low preload should be supple, and for many riders they bottom the suspension in this case. You (like me) are relatively light, so you don't have to worry about bottoming your suspension in all likelihood. Take the stock pipes off and put a lighter (but expensive) set like a Zard, and you make the suspension work less as well.

Suspension is likely the first thing you will want to change, but there are plenty of people who are happy to live with the stock suspension on a daily basis.
 

·
Registered
Joined
·
366 Posts
Keep a wrench in your jacket and try it for yourself. I found that actually less pre-load gives me a more "supple" ride on the fork. I have 5 1/2 lines showing, but was down to 6 showing for a while. I am still playing with it and I weight much more than you do with gear. The link that NorthernThrux included is a great source of info.
Oh, replacing the rear shock has made a huge difference in the ride for me. I have a rebound, length and pre-load adjustable set of Ohlins on the rear TR538s I believe, great shocks. I will be moving on to the fork shortly.
 

·
Registered
Joined
·
1,408 Posts
There are a couple things I would like to add to NorthernThrux's treatise above. The sag percentage for a sporty bike is often less than thirty percent. One half to one inch is considered about right for many. This will minimize fork dive and wallowing, but still give you suspension that may react in either direction. If you cannot achieve the desired sag with the stock spring, it can be altered to produce a higher overall spring rate by cutting off about a half an inch and replacing the removed spring with a pvc spacer. Removing coils will shorten the available amount of wire and stiffen the rate. This does shorten your available travel before the spring binds, but it is an economical way to change your spring rate. However, many of us just bite the bullet and purchase a progressively wound set of springs. At just over a hundred dollars, this is a super way to really improve suspension action, handling, and braking...
 
1 - 7 of 7 Posts
Top