Back end setup, need help.

[Phalophalot]

Got a problem with bike set up as far as the back end of the bike wants to slide out and overtake the front end.
Noticed it first at coffs on practice day. I avoided the 30fter due to the rumours of a puddle before the ramp.
When fanning the brakes on the 'B' line the rear tyre slid out from under me. Track was wet but front end stuck like glue

Again on the weekend at Ourimbah in dryer conditions. light fanning of the brakes and I noticed the back tyre lost traction & was trying to slide out from under me.
This occurs while cournering of course. But the rear tyre was at no point locked up.

Any suggestions on the problem.
My bike has a longer than average wheel base.
Shock -Fox DHX4
My rear tyre is a near new Holy roller.
My thought is that when the fork sags under breaking the rear end is not moving quick enough to compensate for the changing angle of the bike.
So could it be dampening too slow??
Any other suggestions for set up?
Oh yeah, Cletus has cursed me with his former black metal satanic whitchdoctor abillities with the curse of 'three runs one flat tyre.' So I have to run my rear tyre pressure harder than I'd like to compensate for his evil magic.

Any tip you racers out there?? Cheer's

[treggs]

A new holy roller on the back running reasonably high pressure..... I think I found your problem. No side knobs and high pressure will make it pretty nasty....

[Phalophalot]

Cheer's. That might be a simple solution.
I did notice The gun Brad Kelly had Minions front & back. I'll look into that for sure.

[Kreaky]

Umm, Do you mean High Roller??

If you are running a Holy Roller then you problem is right there! Holy Rollers are DJ and street tires, not DH tires. If I where you I'd go out and purchase a Minion front and slap it on the back. I find that it helps keep the back wheel from sliding during cornering more so then other tires.

But seriously, What are you doing running a tire with no side knobs for DH??

[Phalophalot]

[QUOTE=Kreaky]Umm, Do you mean High Roller??

If you are running a Holy Roller then you problem is right there!

Uhh, sorry. I mean High roller.
Front Minion for back hey..
I use front Minion for front & it is awsome. Never considered it as a back. Is this the norm for elite riders??

[scblack]

=Phalophalot
Uhh, sorry. I mean High roller.
Front Minion for back hey..
I use front Minion for front & it is awsome. Never considered it as a back. Is this the norm for elite riders??
A lot of elite guys do use the minion front on the rear.

It's also a way to rotate your tyres - once the rear wears down, move the front to the back, and replace the front tyre.

[---Matt---]

I think it's gonna be a combination of the high roller not being the best tyre out there mixed with possibly too high tyre pressure. What pressures do you run while racing?

Also, how fast/slow do you have your compression/rebound on your rear shock? If you have it too fast the rear will stutter out of control and if you have it too slow the rear won't react fast enough.

Oh, and a front minion on the front and rear is a very good combination at good value for the $$$

Did this help at all?

---Matt---

[orange_222]

one cheaper fix may be to run less pressure with the duel ply high roller tire and put a downhill tube in. also you mite want to split another tube down the middle and put it around that downhill tube. and run lower pressure. i cant see that puncturing easy and my mate runs high rollers on the back on his bighit with no problems and thats when there bald. hope that helps

[Phalophalot]

Thanks for the advice MATT & Orange 222 & all else with those hot tips.
It seems Tyre pressure & Tyre Choice is the concensus on this problem.
Not sure what pressure my rear tyre is exactly as I just use the thumb test but I'd say its roughly, 35psi.
I'm only a light guy at 65-70kg so you'd think I wouldn't get to many punctures. But Pinch Flat is my middle name.
Regarding dampening, I have it set so when I drop the bike from off the ground it doesn't bounce when it lands. This was a set up tip I've herd around the traps & thought it felt OK as a set up option.
High Roller Slow Reezy I think its called. It's a tubeless tyre I'm running with tubes. Although I had the same issue with flats on a super Tacky tubed High roller?

[Dirt Devil]

Regarding dampening, I have it set so when I drop the bike from off the ground it doesn't bounce when it lands. This was a set up tip I've herd around the traps & thought it felt OK as a set up option.
I reckon most full squish bikes wouldn't bounce when you drop them, regardless of the settings. Try adjusting your rebound settings during a ride.

It sounds like the rear tyre is your problem though.

[dazz]

Yeah, change your tyre. I was running High Rollers front & back, one day I switched to minions & 90% of the bikes handling problems dissapeared.

[---Matt---]

Thanks for the advice MATT & Orange 222 & all else with those hot tips.
It seems Tyre pressure & Tyre Choice is the concensus on this problem.
Not sure what pressure my rear tyre is exactly as I just use the thumb test but I'd say its roughly, 35psi.
I'm only a light guy at 65-70kg so you'd think I wouldn't get to many punctures. But Pinch Flat is my middle name.
Regarding dampening, I have it set so when I drop the bike from off the ground it doesn't bounce when it lands. This was a set up tip I've herd around the traps & thought it felt OK as a set up option.
High Roller Slow Reezy I think its called. It's a tubeless tyre I'm running with tubes. Although I had the same issue with flats on a super Tacky tubed High roller?
In my opinion 35psi is waaaaaaaaaay to high for DH. I usually run mine between 15-20psi on smooth courses and 20-25 on super rough ones. I've found any higher pressures and I get the same symptoms as you. Before you go spending money, head out to a DH track and try out different pressures. You'd be surprised what a difference even 5psi makes.

If you're experiencing lots of pinch flats, I'd firstly check to see if the tyre is single ply or dual ply and secondly, if you're having major problems you could go out and buy DH tubes. I honestly haven't had a pinch flat since running dual ply Maxxis Minions which is going on about 3 years. Oh, and for the record I weigh approx 85kgs.

---Matt---

[top_dog]

Yep sounds like tyre pressures to me. I run High Rollers and love them better than Minions IMO. Steve Peat and Fabian Barel run them even though they are sponsered by other tyre company's.

I run about 20 psi in my rear and about 12 psi in the front and haven't had a flat for yonks. I use DH tubes though, and I go through rims at a frightening rate. I have killed a 729 in 17 runs. Not cool, but like everything its a compromise. I weigh 73kg.

[treggs]

Ok if it's a high roller then it shouldn't be too bad. Try tubeless or DH tubes to stop pinch flats and run lower pressures. Mid to high 20's psi should be fine with a DH walled High roller. If you are still getting flat's .... avoid the rocks :D
Also try slowing your rebound down. A common mistake with rebound is to run it to fast. This unsettles the back. With slower rebound the bike will be nicer to control in the rough stuff and when the back steps out (which you want it to do before the front) it will be easier to catch. Slow rebound also makes drifting easier. Also your high speed compression may be too hard causing the bike to bounce of rocks rather than rolling over them. Back your compression and platform adjusters off a little. One at a time though so you know which one is causing the problem.

[Cletus]

hahahaha, do you know what it was? it's all johnnys fault(kinda) i accidently touched his cursed foes down at the canberra state round and knew if i got back onto my bike straight away i would pass the curse onto my bike, sooooooo..... i got onto yours insted:p sorry for the fall at stromlo dude:D
oh and maybe because your faith is made by GIANT is why it handles like crap?

:mad: cant belive you still beat me at ourimbah:mad:

[Phalophalot]

Cletus, "Back Off!", You & your Voodoo arn't welcome on this thread.
But to all else who replied "thanks alot" you have given me some sensible clues to work off & I promise to take your advice on board which should help my bike's performance. farkin stoked guy's
Cheer's.

[---Matt---]

Cletus, "Back Off!", You & your Voodoo arn't welcome on this thread.
But to all else who replied "thanks alot" you have given me some sensible clues to work off & I promise to take your advice on board which should help my bike's performance. farkin stoked guy's
Cheer's.
Cool! Let us know how you go.

---Matt---

[dh squid]

Dont want to be stating the obvious but try doing all your braking before you start cornering, will get alot more traction if not on the brakes mid corner;)

[Phalophalot]

Dont want to be stating the obvious but try doing all your braking before you start cornering, will get alot more traction if not on the brakes mid corner;)
Your right about that as far as traction goes, but I'm talking racing here & braking before the section I need to slow down in doesn't make sence. I still got to make up almost 30sec before & can even match Brad Kelly. (Ourimbah track)
In moto sport they will tell you that but not so sure when your using just gravity & my seedy legs for power.

[scblack]

..... my seedy legs for power.
weedy - weedy little legs is the word you were after...........;)

[Phalophalot]

weedy - weedy little legs is the word you were after...........;)
Hey man! I know I got chicken legs but on a sunday morning seedy is generally the word.

[No Skid Marks]

Rebound tyre pressure etc yes but also consider
Rim width(for the pinch flat problem).
Too steep head angle(making the rear break to early)combined with the above problems or a combo,oh and what way are you running the tyre?

[lindsay]

Everyone here is blaming the equipment. I think I've only read one comment that commented on riding style. Riding technique is what makes people fast, not the equipment.

As long as your high roller on the rear is near new it will not be causing you to slide out. As for pressures most of the pros run upwards of 25 psi, usually around the 30 mark front and rear. I'm refferring to guys like Minnaar and Hill, not some average joe trail rider.

dh squid hit the nail on the head. Do all your braking before the corner. Your tyre only has so much traction. If your cornering and braking then one of these is going to be compromised.

If your still sliding your rear wheel when your not braking then try shifting your weight back, you've probably got too much weight over the front wheel.

Now if your still sliding after these two points then slow down a bit more before the corner. Slower entry speed often means you can hit the corner smoother carrying more speed out. If you come in pinned and slide you'll be loosing speed through the corner.

As for rear shock set up. It's probably best just to experiment and find whats best for you. Find a section of trail thats fairly rough and continue to ride over it adjusting one shock setting at a time. This way you'll get a feel for what each adjustment does.

Hope this helps.

[Phalophalot]

Nice pointer's No Skid Marks & Lindsay,
do you mean too SLACK a head angle. Meaning due to the long wheel base the rear break is being applied before it gets to the braking point? Please expand on this if I am incorrect.
& Yes I do tend to put more weight emphesis on the front end of the bike, probably learn't from riding a hard tail.
Repositionng weight to rear of the bike is a point no one has mentioned yet. but probably valid. sweet guy's.
still not sure about breaking earlier though.
If one can get both wheels drifting in the right direction sounds quicker for race day.
Anyway thanks for every one's tips. Looks like a wet weekend, perfect for staying home & setting my bike up.
You guy's rock. Cheer's.

[Scott]

If one can get both wheels drifting in the right direction sounds quicker for race day.
Any loss of traction is not quicker... sure some pros do some drifts in race runs, but its not by preference, its because they cannot prevent it. Just because you see two wheel drifts in videos doesn't mean they do it (intentionally) in race runs.

[thecat]

Your right about that as far as traction goes, but I'm talking racing here & braking before the section I need to slow down in doesn't make sence.

Yes it does. Braking in or through the corner is silly. You need to set your speed in the approach to the corner then get off them.

Most of the elite guys have braking markers, ie a tree or something that they use as an indicator "Ok get to the tree brake hard then off for the corner"

[scblack]

phalophalot, the High Roller could be a part of the problem too. I am finding that the High Roller on the front of mine seems to wash out much easier than the Minion I used to use. I THINK its because the knobs in the middle are much wider, seem to slide sideways easier, and do not DIG in like the narrower knobs of the Minion.

I am getting a couple of DHF super tacky minions this weekend to try to address my issue.

[Cave Dweller]

phalophalot, the High Roller could be a part of the problem too. I am finding that the High Roller on the front of mine seems to wash out much easier than the Minion I used to use. I THINK its because the knobs in the middle are much wider, seem to slide sideways easier, and do not DIG in like the narrower knobs of the Minion.

I am getting a couple of DHF super tacky minions this weekend to try to address my issue.

I find the same, but i think it is due to the side profile of the tire more then anything.

If you look at a high roller side on there are sections of the tire where there are no knobs present and you can see from one side to the other, compare this to a minion DHF and the whole side profile is full of knobs, this is why they don't slide out as easy, there is no easy path for the dirt to get from one side to the other (like when the tire is sliding sideways).

[scblack]

I find the same, but i think it is due to the side profile of the tire more then anything.

If you look at a high roller side on there are sections of the tire where there are no knobs present and you can see from one side to the other, compare this to a minion DHF and the whole side profile is full of knobs, this is why they don't slide out as easy, there is no easy path for the dirt to get from one side to the other (like when the tire is sliding sideways).
Yep, makes sense - there is much less ability from the knobs to stop sideways motion/dirt/sliding.

Combine the "channels" you are seeing, with the knobs being much wider across the tyre (which means less edges there to dig in), and it's lateral/steering/sideways grip has to be reduced compared to a Minion, I reckon.

[WolfCreekPsycho]

Hey guys, just thought i'd throw my 2 cents in regards to braking mid corner... i have spent a fair bit of time at the race track and there is a lot of theory behind braking into a corner that is applicable not just to road/race bikes but to any bike with suspension.

Now i havnt been riding downhill long and dont claim to be very fast...but..the theory is still the same.
There is a technique called slow in fast out that essentially means brake before the corner so that the bike and the suspension are all balanced and settled for you to take the corner... and forces (G's) applied whilst cornering will be applied to both wheels equally and a 50-50(weight balance will be achieved until you hit the apex and wind the gas on)

There are 2 major points that cross over to mountain biking straight away:

Weight balance:
No brainer here.. hit the brakes and your body weight will want to keep going in the direction its heading.... if thats different to where you want to go, then you are losing energy, momentum and exerting additional sideways force on your tyre.
We all know that this unweights the back tyre too which means your that supreme suspension setup you worked all week on getting just right is now pretty much useless. (with less weight now on your rear, the compression will seem to stiff and cause it to skip and bounce.)

Suspension:
If you take the time to set proper sag levels (preload) for your bike then whether you are cranking through a berm or a rutted corner, you want maximum available travel from both front and back shock.. not just to soak up the bumps, but also to stay in contact with the ground over ruts and dips in the track, cause when that wheel is not on the ground, then its not doing anything right ?
So this sort of follows on from the weight transfer issue, Load your front forks (brake dive) and you have just lost a heap of travel for any bumps mid corner (even worse if you have progressive springs)
If you are unloading your rear shock, then it will start to reach its max travel length so that there is a greater chance of your rear wheel being off the ground after any bump, root or dip.
If this is happening whilst you are trying to turn, then you know what will happen. : )

Maintain an even weight and suspension balance you will definately notice a difference through corners....

Now if only I didnt ride like such a wuss I could show you what I mean
; )