# Rear traction on loose climbs



## moshemark (Mar 1, 2007)

I weigh 120 pounds and my son--the stoker-- weighs 64 pounds. We ride a Ventana ECDM with Nano Raptor tires inflated to 35 psi (not tubeless).

I find that on steep climbs with loose rocks, the rear wheel spins out fairly easily. My guess is that this is partly due to the light weight of the stoker. Do you think that a freeride type tire may help? Which one? Any ideas how to deal with the light weight of the stoker?

Thanks.
Mark


----------



## dodger (Feb 10, 2004)

*stoker weight back*

Have your son try to shift his weight back on the seat. It's counter to the normal single position as you would just tend to wheelie on a single.

That said, there's no point in going with weight wheenie anything on a tandem, especially tires. We run the biggest baddest tires we can get. Even with 7" in the front and 5.5" on the rear of our ECDM, we're still just plowing into stuff instead of floating over it. Burly tires are a must on the tandem. Find some that are not ramped. The ramps lessen rolling resistance but at the expense of climbing traction.


----------



## twd953 (Aug 21, 2008)

I'm a bit heavier than you (170 lbs at the moment) but also ride with my kids in stoker position and they range from ~40-80 lbs.

Definitely have less rear wheel traction than with an adult stoker, but even with the kids can sometimes get up some stuff that I don't always make on my single bike.

What size tire are you running? Personally, I dont run anything smaller than a 2.3 on tandem if I can help it. Will ride up to 2.5" downhill tires. I like the extra volume and the sturdier tire casings.

Tire pressure is also very important, just like on a single. In general, the larger the tire, the lower the pressure you can run, the lower the pressure, the lager the contact patch, the better the traction. 

In your case, I'd suggest larger tires, and lower pressure. 

Or at least experimenting with your tire pressure. Try lowering your PSI a couple PSI at a time and see how it feels. Keep lowering it the PSI until you noticing the tires starting to squirm/fold over or bottom out on roots/rocks. You have to use some common sense here so you don't crash or damage your equipment, but you get the idea.

On a single bike I rarely if ever run more than 20 psi (tubeless), sometimes less than 15 psi, but I can't run that low on tandem. I find on tandem, even with a child stoker, keeping the tires from folding over at lower PSI is the limter more so than avoiding bottoming out the rim and pinch flatting. I find the front tire on tandem is a lot more prone to folding over than on single since you don't have a lot of control over front/rear tire weight distribtion like you do on a single. This is particularly noticable in off camber sections and tight switchbacks.

The larger free-ride/downhill oreiented tires tend to hold their shape better than light weight XC oreinted tires. 

As to climbing technique, as was mentioned, have the stoker lean back a bit, and you can do the same from the captain positions to an extent. Every little bit helps.


----------



## PMK (Oct 12, 2004)

Less rear shock pressure may also help. This will allow the bike to squat more and find more grip.

Overall though, the entire machine is very light and has minimal weight pushing the tires tight to the ground.

In jest I suggest long hoses on your Camelbacks and a rack to mount them over the tire.

PK


----------



## moshemark (Mar 1, 2007)

PMK said:


> Overall though, the entire machine is very light and has minimal weight pushing the tires tight to the ground.
> 
> PK


But when I ride my Ibis Mojo, it's a light machine yet grips really well. (Admittedly, I'm using wide tubeless tires which I run at 20 psi.) So I have to figure out how a tandem is different from a single bike.)

Mark


----------



## PMK (Oct 12, 2004)

moshemark said:


> But when I ride my Ibis Mojo, it's a light machine yet grips really well. (Admittedly, I'm using wide tubeless tires which I run at 20 psi.) So I have to figure out how a tandem is different from a single bike.)
> 
> Mark


The techno way to describe this is called weight bias.

The percentage of weight on the rear wheel of the IBIS is greater than the percentage of weight on the tandems rear wheel.

Motorcycles deal with this by moving the rear wheel forward or aft to alter the front grip.

Take two fairly accurate bathroom scales. With gear on, sit on the bike, have someone steady the machine without forcing additional weight into the scale as best as possible.

Record the front tire weight and rear tire, then the percentage on each tire.

Do the same for the tandem with both riders aboard.

The tandem will have a front bias a lot more than the single.

Consider where the center of gravity is for both machines. This then relates to why the tandem can not shift the weight aft, driving the tire into the dirt (rocks).

PK


----------



## banks (Feb 2, 2004)

moshemark said:


> *Nano Raptor* tires inflated to 35 psi (not tubeless).
> 
> I find that on steep climbs with loose rocks, the rear wheel spins out fairly easily. My guess is that this is partly due to the light weight of the stoker. Do you think that a freeride type tire may help? Which one? Any ideas how to deal with the light weight of the stoker?
> 
> ...


There is the problem in bold. Get a tire that has more square edge knobs with much more spacer between the center ridge tread; Specy Captain, Specy Purgatory, Etc. But with the power of 2, almost any tire can spin. My wife and I can spin the IRC Kujo DH 2.125 rear tire at 35psi with a tube and that tire really hooks up.


----------



## moshemark (Mar 1, 2007)

I'm considering putting one of these tires in the rear to deal with my problem:

Minion DHF EXO 2.5 (Maxxis Minion DHF EXO Tires 100065564 at CambriaBike.com)
WTB Dissent 2.5 (Steel)
Conti Diesel 2.5
WTB Weirwolf 2.5 Kevlar

Which do you recommend?

Thanks!
Mark


----------



## TandemNut (Mar 12, 2004)

moshemark said:


> I'm considering putting one of these tires in the rear to deal with my problem:
> 
> Minion DHF EXO 2.5 (Maxxis Minion DHF EXO Tires 100065564 at CambriaBike.com)
> WTB Dissent 2.5 (Steel)
> ...


The Wierwolf is a better front tire than rear. You don't necessarily need a heavy DH tire with your total team weight, but try an aggressive XC/FR tire like WTB Bronson or Kenda Nevegal (turned backward); both are kevlar bead, somewhat light, and will do better. The Mutano is a grea tire for dry hardpack, and is very fast-rolling, but is no good in loose or wet stuff. 
Also, if the stoker wears a camel back, it actually helps. In fact, I was surprised how much difference it made when my kids leaned back during steep, loose climbs; much more impact than I would have thought. Especially when they weighed 1/4 - 1/3 of what I weighed.
PMK is right about the suspension too; a bit of fine tuning there may help.


----------



## moshemark (Mar 1, 2007)

I have a limited selection here of 2.5 tires at reasonable prices. What about the Maxxis Minion DHR 2.5 two-ply?

Thanks.
Mark


----------



## Okayfine (Sep 7, 2010)

We are one of the heavier teams at ~360 for riders+gear. We still have issues with rear traction at times. As mentioned, much of it is about stoker positioning. Most of the time it is a non-issue, but certain trails are loose enough and/or steep enough that I have to tell my stoker to move back on the seat. This helps a lot.

Tires are also a factor. Because of our team weight we run 2.5 Dissents. They work well in SoCal conditions - hardpack and loose rock. They're not good mud tires. You will probably notice the weight of the carcasses due to low team weight.

One last thing is cadence - on steep/loose or technical climbs, if we keep cadence high, climbing is much easier and there's a much smaller chance of spinning out. If cadence is low, you're mashing each pedal stroke over center. This causes peaks in power delivery and those peaks can exceed available traction.

When we get into discussions about the tandem, people are in disbelief that we ever have rear traction issues.


----------



## moshemark (Mar 1, 2007)

Okayfine said:


> One last thing is cadence - on steep/loose or technical climbs, if we keep cadence high, climbing is much easier and there's a much smaller chance of spinning out. If cadence is low, you're mashing each pedal stroke over center. This causes peaks in power delivery and those peaks can exceed available traction.
> 
> .


That's interesting. On a single bike, many people advise to choose a harder gear / lower cadence when going up the rough stuff. (See, for example, What Is The Efficient Cadence for Mountain Biking? .) Why is it different on a tandem?

Thanks.
Mark


----------



## arly (Apr 20, 2005)

Mark, What these guys have said, we'll have to agree with. We're around a 300lb team and we use the largest, most knobby tires we can fit on. Today we've running Nokioa 2.5's on the rear. Nonetheless your rear weight and overall team, weight is so low, you will spin out long before most tandems will. As you state and your teaming being sooooo light, you may need to resort to single bike technique to keep the spin in check. We call them 1./2 bikes 
Hope that helps!


----------



## Okayfine (Sep 7, 2010)

moshemark said:


> That's interesting. On a single bike, many people advise to choose a harder gear / lower cadence when going up the rough stuff. (See, for example, What Is The Efficient Cadence for Mountain Biking? .) Why is it different on a tandem?


The link seems to be overly concerned with butt comfort 

My experience above is not necessarily indicative of proper MTB technique, tandem or otherwise. But it does work for us. We've cleaned stuff with the fast cadence (low speed) that we won't clean with a higher gear and lower cadence. Typically anything with either a loose/steep climb or a rocky/steep climb, we're much more successful with the lower-torque method. Switchbacks, especially, are much much easier for us with a faster cadence. Learned that trick from Team Zibell.

Off the top of my head, I'd point to the power output as being a big difference between single and tandem riders. On a tandem you've got more power being put to the rear wheel than you would have on your single bike (and a stoker who can't judge their output because they can't see forward). This is even more evident when you have an adult stoker (and that much more power).

There's also the momentum factor. On a single bike you can use a fair bit of body English to affect the bike's path. I don't do much of that on the tandem, and in large part (hopping the front or back wheel) it's virtually impossible. If you're climbing a steep, rocky bit with a low cadence and you don't have enough momentum to get over the rock your front tire just hit - for us anyway, that means a loss of momentum and a dab. The higher spin rate helps us keep rolling over stuff without having to peak the power (and then lose traction).

Combine that with bigger-volume tires and you keep moving, keep rolling. If you can keep moving forward you've got it. If you get stopped, that's generally a dab. Then there's the higher center of gravity - once we do lose traction at the rear, 80% of the time we have to stop. On a single bike 80% of the time I can keep going.

When people ask us what it's like to ride a tandem, the best description I have for it (aside from "FUN!") is...different. Some things are harder, some things are easier, but virtually everything's different.


----------



## banks (Feb 2, 2004)

The DHF Minion is a known killer rear tire. What ever you choose, you will need a square tread block for ultimate climbing and braking traction. Weirwolf is a slow rolling tire. The Diesel/Gravity is a great tire but wears very fast IMPO. Dissent is heavy but supper grippy!

Look at the Specy Eskar.


----------



## ds2199 (Sep 16, 2008)

Get a 29er!

I say that in jest b/c I know that is not in the cards for most... But having more tire contact on the dirt just plain works! It is applicable to both tandems and 1/2 bikes.

Also, we have had good luck with the Kenda Nevegals, Panaracer Rampage (2.35) and the Maxxis Ardent (2.4 - this is a big tire). I will add that we have been riding the Velocity P35 rims and the wide rim really makes the higher volume tire fill out differently (better) than the narrower rims. 

In the end, it is different strokes for different folks. 

Specy Eskar rode very nice, but I recall that we wore it out pretty quickly. Same probably said for the Rampage...


----------



## Fleas (Jan 19, 2006)

moshemark said:


> I weigh 120 pounds and my son--the stoker-- weighs 64 pounds. We ride a Ventana ECDM with Nano Raptor tires inflated to 35 psi (not tubeless).
> 
> I find that on steep climbs with loose rocks, the rear wheel spins out fairly easily. My guess is that this is partly due to the light weight of the stoker. Do you think that a freeride type tire may help? Which one? Any ideas how to deal with the light weight of the stoker?
> 
> ...


This is always a tough spot, even on a single.

In addition to running some chunkier tires at low pressure, sometimes the captain has to control the pedals a little more to prevent spiky torque that causes lost traction.

Apply the same pedal skills that you use on your single to smooth out your stoker. It'll be easier since they don't have tree trunks for legs yet. 

btw - since your combined team weight is about my weight, for reference, my tire pressure is around 25 psi for 2.1" to 2.4" tires.

-F

edit: check these out! $22!!


----------

