Another Wheel/Tire/Rim/Air Pressure question.
 

I have read a lot of the information here about wheels, tires, rims … but cannot decipher enough to answer my question. The combined knowledge here has fixed many problems for me before so I am going to toss out another for comment.

Information:
Bike: Santana Team Scandium 8350 miles.
Current Wheelset Hadley/Velocity Fusion (?) Rims 1,750 miles
Previous Wheelset Santana Sweet 16s 6600 miles
Tires on both wheelsets Conti Ultra Gatorskin 25mm at 120 psi
Team weight with Sweet 16’s was around 310
I gained 20 lbs about the time we got the Hadleys

Issue:
With the Sweet 16’s I almost never felt my stoker move around. Since we installed the Hadley/Velocity’s it is like she is driving the bike from the back, I feel like we are all over the road. We have discussed this calmly several times (not so calmly a couple of times), she is certain she is not moving any more than she did last year.

So the question is why did the handling change, and can I do anything about it? (Returning to Sweet 16’s is not an option)
It is time to buy new tires…
Will 28mm tires make a difference?
Will changing the air pressure make a difference?
I am starting to drop the weight, but a 10 lb loss does not seem to have changed the handling.

any and all ideas welcome
thanks

Jack

Out team weight's 290 and use 110lbs. Different rim profile, making the tire come more to a point at the contact patch. Or, mabey not enough air, making the rear a bit squirmey?

Is the spoke tension on the rear wheel high enough? I would think 120 psi would be enough pressure.

Just checked with a Park TM-1, with the tires on and inflated.
Front average of 25 all the way, lowest spoke 23
Rear average 25 all the way, 2 spokes read 20

Jack

Spokes are tight then. Just been through the wheels on our Co-Motion with Velocity rims and a Park TM1.

Try another pump or gage to just be certain they are properly inflated.

Does the bike have a rear rack or bags? I know I can feel every ounce of luggage. Yes you adapt, but it is still noticeable.

I assume you also gave the wheel a side to side flex test when in the frame to ensure structural integrity of the frame and wheel security.

PK

How many and what diameter spokes?

We were a 310 lb. team when we bought our tandem. It came with Aerohead 36H rims. I replaced the rear Aerohead with a Deep V very soon because it was worn. Thinking back on it, we did have less trouble standing with the Deep V. I thought it was just that we got better, but maybe the rim did have something to do with it. A deeper section rim should help.

We also run 25c at 120 lbs. No problem. With our 19mm Deep V rim, 28c feels more squirrelly to me than 25c at the same pressure, but that could just be my choice in tires.

Good catch on the spoke size, I assumed and possibly assumed wrong he was running round 2.0mm spokes for that tool reading.

PK

OK let me see.
PMK: Will find a gage to check pressure. No rear rack or new bags. Just tried your flex test and I don't see anything that bothers me (not good to assume with me).

Carbonfiberboy: 32 round spokes, unsure of diameter. Wheels were purchased from Mark at Precision Tandems I went with what he recommended. Your 28c observations are interesting to me. I wonder if others have had the same experience.

Thanks
Jack

If you have a Park tensiometer, it should have a round spoke diameter gauge that comes with it, as well as a plastic chart that reads out Kgf from the meter readings and spoke diameters. Measure spoke diameters in the middle of the spoke. You could also use a mic. The question is whether you have 2.0mm or 1.8mm spokes.

32 spokes is not a lot for a tandem. We are about the same weight as you and have 36, which seems more standard. Many folks have 40. I know some racers run 32, but I don't know the details of their wheel builds.

Why do you choose 25mm tires?

28mm tires have less rolling resistance, better load carrying capacity, and can run at lower pressures. Sure, the aerodynamics of a 25mm tires will be better, and because of that the 25mm will start to become faster above 25mph. I certainly like having a little more volume under my wheel on a tandem.

Our team is also 310 - 320, and I like our 28mm Ultra Gator Skins at 120psi. In any case, I also feel any movement she makes.

If that's directed at me, we ride 25c for a variety of reasons:
I like the feel of the bike with that tire and rim combo, especially when pushed hard into corners.
Some tires I like very much don't come in 28c.
There is much more variation in rolling resistance between tire models than between widths.
I don't worry about either rolling resistance or tire wind resistance once we can out-coast everyone we ride with. A simple metric.
I don't worry about load carrying capacity as long as we never have a pinch flat. Another simple metric.
If we weighed more, we might choose different tires.
We tour loaded on 28c, same metrics.

I suppose I should mention that I notice Stoker when she goes for a bottle, a very small amount when she signals, otherwise I don't notice her at all, other than through the pedals. We had a very bad test ride on a CoMo Primera, which almost put us off buying our Speedster. I thought at the time it was that the captain's cockpit wasn't set up for me. Now I think it was a tire/wheel issue on the LBS test bike that caused the abominable stoker steering.

To the OP (Just Me), where are you with your tandem's handling issues?

Just stumbled onto your post and was curious what, if anything, you'd been able to learn / resolve.

I haven’t updated because I need to talk with Precision (they were out of pocket for a while) and at the moment there is not a lot to add. I will be ordering Ultra Gatorskins in 28 this week and will report the change when I have those installed.

Still haven’t checked the gauge of the spokes, but I will do that this weekend. I hope the 32 spoke wheels are not the problem.

That is what originally came on our bike, and that is what I have always used. We rarely have flats, I saw no reason to change.

Interestingly enough, after the last conversation with the stoker the handling has calmed down somewhat. I hope to have a more comprehensive update in a couple of weeks after we log some miles with the 28’s.

Jack Allen

I have found that stoker movement is directly related to stoker discomfort which is also related to stoker general fitness.

Lower than normal fitness results in less force on pedals which relates to more weight on the saddle and arms therefore more movement on the back of the bike.

This applies to captains too....
It is not always about the bike

Wayne

FWIW, sometimes our bike is like a tourist bus, squirming back and forth at each new site. Other times, it's as stable as a train on true tracks.

Often one word restore the steadiness, "focus". When I mention she is not riding relaxed or not focused and looking around, many times the stability is restored, just by asking.

PK

Maybe your stoker is working harder to haul your fat a** ;-) Seriously though I notice a big difference when more weight is on the tandem regardless of where it comes from. We just came off a 5 day tour and the bike feels so squirmy the first time you set off loaded, I kept checking for a flat the first day.

Remember its always the captains fault, the stoker is always right :-)