New Trek superfly 9, 2015. Problems setting it up.

[merlinxlm]

Hello everybodyp. I've just treated my self to a bike upgrade, I decided to buy a Trek superfly 9, 2015. I'm happy, but not 100% with the bike. Just can't get it to handle right, feel's very twitchy. I've changed the stem to a 70mm, adjusted the forks to 70psi. The bike shop changed the tyres to, BONTRAGER XR4 TEAM ISSUE TLR MTB TIRE 2.3. I weigh 91/2st, as the tyre/wheel has been setup tubeless. I'm running 20psi, both front and back. Its slightly better, but not as nice as my old Whyte 19. Any recommendation on the setup very appreciated. I am thinking of replacing the stem for a 90mm, I like the streched style setup. Will this longer stem affect the bikes handling?

[scant]

personally I'd make small incremental changes, 1 at a time, until you're happy. adding 20mm to a stem length is a big change (unless you're already used to 90mm stems?)
generally longer stems make a bike feel more nervous & "twitchy", while shorter stems make the bike steer slower, but feel more stable & compose on rougher trails & at higher speeds

[tonytourist]

Can you describe your setup a little more?
I have had two Superfly 9 FS and a Superfly 9 HT. With the Bontrager tires, I found I had to run less pressure than I normally do to get them to feel right, but once I did, I really liked them.

[DanW]

As others have said small changes can make you go from "oh sh1t" to "dialled". If I lower my stem by 5mm everything seems to be thrown out of whack for example.

The bike not feeling sure footed could be a number of things. Usually for me it is being too "on top" of the bars (i.e. stem too short and too low)

It sounds silly but the easiest thing to do would be to copy the set up on the bike you were happy with...

generally longer stems make a bike feel more nervous & "twitchy"

Wrong way around Scant Short stem results in faster steering feel than a long stem.

I found I had to run less pressure than I normally do to get them to feel right

Same here on 2.2 XR2's and XR3's. I am a fair bit heavier than the OP at 80kg and run 21psi front, 23psi rear. I think you could go even lower as the sidewalls are very supportive.

[wingguy]

Everyone is mission the obvious here, the Whyte 19 has a 67.7 degree head angle, the Superly has a 69.7 degree head angle. You're going from a trail geometry steel frame to a cross country rocket carbon frame - it is designed to feel sharper and twitcher and nothing you can do will make the superfly as composed and stable as the 19.

That said stem length and bar width can be used to take the edge off. What is the width of the bar on the Trek?

[merlinxlm]

I'm thinking of trying 18 front and back. As with 20psi, they still feel very hard.

[Gullholm]

Everyone is mission the obvious here, the Whyte 19 has a 67.7 degree head angle, the Superly has a 69.7 degree head angle. You're going from a trail geometry steel frame to a cross country rocket carbon frame - it is designed to feel sharper and twitcher and nothing you can do will make the superfly as composed and stable as the 19.

That said stem length and bar width can be used to take the edge off. What is the width of the bar on the Trek?

This, the geometry and especially head angle plays a big part here.
Except for stem length and bar width, do you know if your bar height is lower than on your Whyte? Many have trouble feeling confident on the bike if the handlebar is too low, maybe even more so than on a stem that's a bit too long.

Often the recipe for getting a bike to feel a bit more comfortable and confidence inspiring is going shorter and higher, for riders who don't want a very race inspired setup. So if your stem is already in it's highest position, maybe you could borrow/try on a riser handlebar? Different handlebar models also have a different feel to them because of different up- and backsweep.

[DanW]

Both frames are reasonably slack by XC standards and there isn't toooooo much in it in practical terms between the two. Whyte don't give a huge amount of geo information out but at a quick glance it looks like the Whyte should be quite a bit shorter for a given size than the Trek. TT's has extended significantly in the last few years. Seat tube angle also looks a degree or so steeper on the Trek. Combining the two have you perhaps shifted your saddle forwards too if the Trek initially felt a bit long placing you even further over the front of the bike?

Generally too much weight over the front of the bike (some combination of current bars being too close and low and/ or sitting further forwards over the BB) is my gut feeling on the cause of the "twitchy" handling too.

[wingguy]

Both frames are reasonably slack by XC standards and there isn't toooooo much in it in practical terms between the two.

Bro, you trippin!

[merlinxlm]

Its more of the lack of front and back end grip. Compared to my old bike, that I' m finding difficult to sortout. Any ideas?

[TheRookie]

If it's a lack of grip at both ends then it's down to tyres and nothing but tyres, changing the riders position only changes the balance of grip.

[DanW]

^ Sounds fair to me.

What tyres were on the Whyte?

[wingguy]

If it's a lack of grip at both ends then it's down to tyres and nothing but tyres, changing the riders position only changes the balance of grip.

Fork setup can also affect front end grip, and shock setup or frame stiffness can affect back end grip. But yeah, normally I'd agree that a general lack of grip is down to tyres, except that it's a totally different complaint to what the OP forst mentioned which was twitchiness.

I think at this point the OP needs to have his problems diagnosed by someone who is actually riding with him in person. (Plus an element of just getting used to a bike which is naturally significantly twitchier.)

[merlinxlm]

I had Panaracers fire pro tyres, 2.10.

[TheRookie]

Well the Bonties should be a lot better than them!

Perhaps if you could describe in more detail the exact issue you have.....break it down for a corner, braking, dropping it in, stable cornering and then straightening out and applying power, what happens in each phase you do, and don't, like.