Bike feels "wallowy" in high-speed corners +Brakefade

[mr2peak]

What's the cause of this?


Current Setup:

Rear shock with sag adjust, it was put on by the PO (or the guy before). Think it's a newgen, not sure.

Front is stock with .70kg springs and Fox SAE 15wt

Rearsets/stripped-cafe'd/re-jett/yoshimura 2-1/pods/clips/lowered frontend/EBC HH pads/and a few more things..


Is it frame flex? Lack of damping? Am I just not 100% smooth? I'm also a lighter person (135ish no-pants-party style) so I doubt it's frame flex. Every time I go for a fast run I loose traction during exit at some point and I managed to hit brake fade on the front a few days ago during a long windy downhill section (****ing terrifying and almost had me in a ditch). Am I running up on the limits of the bike? I don't feel like I need more power because I'm usually on very tight roads and I'm not really a straight-line speed person, more of a momentum driver (DH bike racing background).

Used fox rear shock worth the investment? Should I swap out to an SS bike front fork (like gixxer) and run 1/2 the brake package?

A new bike isn't in the cards for me now, but a few hundred dollars are on the table.

[csmith12]

My best guess based on what you posted James... SS front line with the pads you have now, and bleed the sh*t out of them. If they are not stupid firm within an inch of lever action, they are not right. A few members who have felt mine will vouch for this.

Do you bottom out the front under braking? Hard to spec out a front set up on so little info. What tires you runnin'?

[mr2peak]

Speed Demon tires. Anything stickier available that's not race specific? 16"...

Already have SS front lines. I've bled them properly a month ago, even installed the speed bleeders to help with the process. Flushed the system, went for a short ride, then took my time and flushed/bled again. I don't believe I'm bottoming out the front fork under braking, but I'll zip-tie a stanchion and see where that leaves me. I already have stiffer springs and thicker oil, and I seem to run out of grip before the rear leaves the ground with proper weight transfer when heavily braking. Rear certainly feels light at points though.

[jenkem]

Brake fade can't really be helped without completely re hauling the brake system. Part of the reason super sports have two disks is to help distribute heat.
I think you should get some race tech emulators for the forks, they add a lot of sophistication to the front end dampening. wallowing might be caused by an imbalance with the bound and rebound (or just the lackluster compression capabilities of damper forks). emulators are the bees knees.

[adouglas]

Engage in some troubleshooting 101.

Before you go and start replacing stuff, make sure what you have now is in good shape and adjusted properly.

Sounds like you have two separate issues: "Wallowy" feeling and brake fade.

Brakes: Fading means you don't have enough braking force. So ask yourself why. The stock parts are perfectly capable of stopping the bike without a huge amount of fade, so you don't NEED a brake upgrade (though you might want one anyway).

When was the last time you changed fluid? It should be done periodically. Have the brakes been properly bled? Are the brake pads and calipers in good shape (i.e. are they moving freely)? When was the last time the hoses were changed? This is all normal maintenance stuff.

Wallowy feeling: The stock pregen suspension is soft, but few complain of it feeling "wallowy" at speed. So something is wrong. Again, look at what's there and make sure it's right before you replace anything.

Is your frame in good shape? Cracked? Are the suspension mountings all intact and properly torqued (ask yourself what a loose shock mount would feel like)? How about the wheels... are the axle nuts on securely? What about the swing arm pivot and shock linkage?

Are you sure about all this stuff? Have you actually looked and put a torque wrench on it?

Is the preload on your replacement shock set correctly? At your weight you might want to back it fully out.

You're very light so chances are you don't need stiffer springs. Check your sag and do the zip-tie trick to see if your forks are bottoming out.

When was the last time the fork oil was changed? That too is a routine maintenance item.

Are your tires properly inflated? Before you say "yes," have you actually checked?

You said the front has been lowered, but you didn't say the rear was. Lowering only the front will change the bike's geometry and make it less stable. The more the front gets lowered relative to the rear, the less stable it is. Easy to check... Drop the fork tubes back to stock height, go for a ride and see if it feels better.

Bottom line: Eliminate all possible causes of weirdness one by one. That will tell you if you really need to change things.

[csmith12]

Hmmm... Mr. Fist has a good point. I would ensure the basics are taken care of as I (we) sometimes assume they are.

I have only felt frame flex mid corner, right past apex with a pinned throttle. I describe it as a humping feel. It's like the bike humps through the corner as the frame flexes near the head. This is on my newgen, since your bike is a pregen I cannot comment on the feel as I haven't pushed my pregen that hard.

.7's with 15w with stock preload should feel pretty good to a rider of 135lbs. Stock rear shock I assume? If so, this could be the source of your wallowing as it may need replaced vs. serviced. Yep, I said replaced because for the $$ spent, it's better to replace it with something else such as a stock gsxr shock. Lowering the front is a common race mod done to the 250's (as you know) but does also require that the rider get the weight off the front mid corner. Since you can't do it 100% with the throttle, then the riders weight and suspension setup must assist. So the two main suspension parts (forks and rear shock) should work together to balance everything out with the rider's preferences/style. Otherwise, the front may feel heavy and push out (want to tuck) or if the rear is too soft, the front can feel null (woodish). Assuming everything is in good shape. Go see a suspension tech and have a baseline done. This should get you in the ball park and you can tweak from there with, oil, preload spacers, valving (emulators/intimidators), ect.. ect...

Your brakes... this last race round, I slid (rear) the bike into corners while crazy late and hard on the front brakes. Your brakes can inspire that same confidence when all is well. Even on crazy hot days and heavy brake usage I have never experienced fade with the same equipment you have. The first thing I would suspect is the bleed job. Sometimes getting all the air out of the system is just a pain in the arse. Try the zip tie trick to force the hard to get bubbles out? Next would be the fluid. I know you flushed it but how old is the fluid, contaminated somehow maybe? After that would be the pads and bedding. Perhaps you got some glazing going on but I doubt it or your comments would not be about fade.

[alex.s]

sounds like lack of damping on the rear shock.

also sounds like you should switch to dot 4 or dot 5.1 to help with the brake fade.

[adouglas]

Originally Posted by csmith12

I describe it as a humping feel. It's like the bike humps through the corner as the frame flexes near the head.

I love it when you talk dirty.

[csmith12]

^^^^ bwahahhahahahahah

[alex.s]

if its a track bike you might consider reinforcing the join at the rear of the backbone diamond across the lateral bar. helps with the neck flexing up. also you can put beefier top radiator/engine mounts on which also helps the floppy neck

[choneofakind]

Brake fade? Braking too much.

Give them a good bleed and work on carrying more speed.

[csmith12]

Originally Posted by choneofakind

Brake fade? Braking too much.

Lol, indeed... they stay cooler when not squeezing on the disc.

[ninja2007]

How many miles are on her? Somewhere around 40k the fork bushings may need a look, particularly if everything else is right.

I had a wallowing front end on a bike, that turned out to be the fork bushings being shot.

If you take the springs out of the forks, do the lower legs wag around if you lift up and down on them?

Another spot to look is the steering head. You might be missing a ball, or have a bit of slop in the groove that you don't feel until you countersteer.

Zach

[ninja2007]

Originally Posted by alex.s

if its a track bike you might consider reinforcing the join at the rear of the backbone diamond across the lateral bar. helps with the neck flexing up. also you can put beefier top radiator/engine mounts on which also helps the floppy neck

Where do you get beefier top engine mounts?

[alex.s]

Originally Posted by ninja2007

Where do you get beefier top engine mounts?

make them

[ninja2007]

Is the mount you speak of the one with the long bolt running horizontally?

Thanks,

Zach

[mr2peak]

Originally Posted by alex.s

sounds like lack of damping on the rear shock.

also sounds like you should switch to dot 4 or dot 5.1 to help with the brake fade.

I bought a GSXR rear shock a few days ago, I'll pull the bike apart and re-torque everything when it goes back together.

I'm going to reinforce the frame in a few places when I get some time. I think the brake solution is going to be a new front end with 1/2 the brake package from a gsxr or similar, all told I think that will cost less and perform much better than a fork brace, emulators, brakets for bigger calipers, new master, etc. I already have all the "suggested" front brake upgrades but it still feels lacking.

[mr2peak]

Originally Posted by ninja2007

Is the mount you speak of the one with the long bolt running horizontally?

Thanks,

Zach

Yes, where that connects to the frame is my guess.