chain tensioners

[LanceT]

Anyone ever had problems with fixed tensioners as opposed to spring.

My fellow Orlando local Brian took this shot at New Smyrna beach a little while back and it looks pretty good. But then my chain caught my eye. I am mid gap and the chain is supposed to be tight, running from the front chainring to the guide pully. But in this pic you can see it looks pretty slack. I know the frame flexes, but I guess it's more than I thought. And this frame is pretty solid in my opinion. The chain doesn't look too safe like that and I have had my King hub skip from time to time. I am wondering if anyone has experienced a similar issue.

Thanks,
LT

[goose]

I have noticed this myself with my tensioner, as it is a rennen inspired design. I don't think it contributes to skips, though, as my King skips with no weight on the pedal, not in the setup for a gap. When I was testing my tensioner off bike, I noticed this for sure. My tensioner is flexier than a rennen for sure. It's made from plate that's half as thick, and I use a lot of offset to clear my chainstay.

http://www.observedtrials.net/album/data/500/DSC01248sm.JPG

I think that in the picture, you've preloaded a tonne, so the top of the chain is wicked taught, and the bottom becomes lose as a result. Also, during the preload stages of gap, I bet the chain stretches a lot on top, so all that slack comes around to underside of the chainring/cog. I bet the tension evens out as soon as you release the rear brake.

I wouldn't call what I've had a 'problem'. Ever since switching to a singlespeed setup with a BMX chain and rigid tensioner, I've had far fewer drivetrain related problems, so, I think it's just the nature of the beast. I've been thinking of a way to make a very strong, out of the way sprung tensioner that is designed to be as tough and tidy as the rennen, but have a small stiff spring in it to keep the chain tension more constant throughout the pedaling motion.

[felix]

Same thing here. When I put a lot of torque down, my chain is loose and hits the chain stay.
It hasn't caused skipping though.

[dubtrialsin]

i agree with goose
in how your chain has slack underneath because of preload.
ill show u my tensioner tomorrow
i havent worked out all the bugs yet but for a fixed tensioner it works pretty well with the halflink chain ive been running
tzimon, philth, and i all run the half-link chains and have no complaints thus far.

[bouncingbabyboy]

I have noticed this myself with my tensioner, as it is a rennen inspired design. I don't think it contributes to skips, though, as my King skips with no weight on the pedal, not in the setup for a gap. When I was testing my tensioner off bike, I noticed this for sure. My tensioner is flexier than a rennen for sure. It's made from plate that's half as thick, and I use a lot of offset to clear my chainstay.

http://www.observedtrials.net/album/data/500/DSC01248sm.JPG

I think that in the picture, you've preloaded a tonne, so the top of the chain is wicked taught, and the bottom becomes lose as a result. Also, during the preload stages of gap, I bet the chain stretches a lot on top, so all that slack comes around to underside of the chainring/cog. I bet the tension evens out as soon as you release the rear brake.

I wouldn't call what I've had a 'problem'. Ever since switching to a singlespeed setup with a BMX chain and rigid tensioner, I've had far fewer drivetrain related problems, so, I think it's just the nature of the beast. I've been thinking of a way to make a very strong, out of the way sprung tensioner that is designed to be as tough and tidy as the rennen, but have a small stiff spring in it to keep the chain tension more constant throughout the pedaling motion.

Your analysis seems pretty fair. You have inspired me. I didn't want to drop a bunch of money on a chain tensioner and a lot of them won't work pushing up with a Zebdi geometry. Yours is sexy and I have the tools. I may have to make my own. :bigthumb:

[LanceT]

I have a test.

Put your front wheel against a wall and stand behind your bike while holding the handlebars. Now step down on the pedal that is your strong foot forward slowly and steadily and don't grab the brakes. Act like you are trying to drive the bike into the wall, but do it in a controlled motion. See what happens.

For me, my chain goes slack and I can clearly see the frame both twisting at the BB and curling up or bowing under the drivetrain torque. If I look at the rear hub I can see the chainstays curling under, or at least that's what it looks like. It's like the tension on the chain is trying to pull the two gear cogs together and crush the rear triangle. Maybe my frame isn't very strong and I have done a lot of shows on it, but I have another one and it is similar, as is my Zebdi. Maybe I am too rough. My frames seem really flexible to me. It also seems to be worse for the right foot forward than the left.

See what you guys think.

[AgrAde]

it doesn't really matter. the only point of a tensioner is to keep the top of the chain tight to keep the engagement good and give you enough chain/cog contact to keep from skipping of excessive wear. the bottom doesn't mean shit unless you have a problem with skipping.

if it's keeping the chain tight until the point where you put the power down, it's doing a good job. just ignore it unless you actually notice it being slack.

[Peace]

yeah i guess thats the advantage of having a sprung tensioner..... sprung is good.

[dubtrialsin]

if it's keeping the chain tight until the point where you put the power down, it's doing a good job. just ignore it unless you actually notice it being slack.

word

lance, give me a call when u want to meet up
do u want to ride downtown or do u have other spots u frequent?

[music_maj_34]

I have a test.

Put your front wheel against a wall and stand behind your bike while holding the handlebars. Now step down on the pedal that is your strong foot forward slowly and steadily and don't grab the brakes. Act like you are trying to drive the bike into the wall, but do it in a controlled motion. See what happens.

For me, my chain goes slack and I can clearly see the frame both twisting at the BB and curling up or bowing under the drivetrain torque. If I look at the rear hub I can see the chainstays curling under, or at least that's what it looks like. It's like the tension on the chain is trying to pull the two gear cogs together and crush the rear triangle. Maybe my frame isn't very strong and I have done a lot of shows on it, but I have another one and it is similar, as is my Zebdi. Maybe I am too rough. My frames seem really flexible to me. It also seems to be worse for the right foot forward than the left.

See what you guys think.

I'm just curious... do you have to use a half link on your set up? I have the same exact tensioner and the only way I can run it is with a half link. I never noticed if my chain gets slack in it or not, I'll have to check it out. Thanks for the post.

[LanceT]

I don't use a half link. On the HIFI I have 22-19 gearing and I think the chainstays are 375mm. It works absolutely perfect, but on other bikes it may not. I tried it on a BT and it wouldn't space out like that. I just got lucky I guess.

I think my main point with the chain slack issue is that the frame is flexing a lot more than I thought and that makes me concerned. I have broken many things and whereas flex isn't necesarily bad, it is something to be aware of. For instance my PX knifen Ti fork is the most flexy thing I have ever ridden, but I have not had any problems.

With aluminum I think flex is more of a concern. Aluminum will break with too much movement. Ti will last longer as it isn't so brittle.

But everything on the HIFI is still in one piece, so that's good.:x:

[Mango]

a spring loaded tensioner would hold that chain down when you preload but the springs wear a lot and can become very rather loose. i find with my fixed tensioner (tensioner seeker) it keeps a tight tension always and has a good tensions between preloads. Where as my old spring load would be a somewhat worse tension all the time.

[goose]

With aluminum I think flex is more of a concern. Aluminum will break with too much movement. Ti will last longer as it isn't so brittle.

But everything on the HIFI is still in one piece, so that's good.:x:

maybe throw down for a custom steel rig then. Professional cirque riders should totally go baller on their ride with custom:)

I thought this popular U6 alloy was supposed to be much more resiliant than multipurpose grade. Are you worried you're going to tear the weld on the non-drive side where the BB meats the chainstay, or something???

BouncingBabyDude: I used a hacksaw, a drill press, and file. 45minutes later, I had that. Dunno about sexy, although cheap and functional is appealing. Sexy may be a stretch. Good luck with yours!

[music_maj_34]

I don't use a half link. On the HIFI I have 22-19 gearing and I think the chainstays are 375mm. It works absolutely perfect, but on other bikes it may not. I tried it on a BT and it wouldn't space out like that. I just got lucky I guess.

I think my main point with the chain slack issue is that the frame is flexing a lot more than I thought and that makes me concerned. I have broken many things and whereas flex isn't necesarily bad, it is something to be aware of. For instance my PX knifen Ti fork is the most flexy thing I have ever ridden, but I have not had any problems.

With aluminum I think flex is more of a concern. Aluminum will break with too much movement. Ti will last longer as it isn't so brittle.

But everything on the HIFI is still in one piece, so that's good.:x:

I have a Hi-fi as well, but I have a 18 t White Industries trials freewheel on the rear and a Middleburn 22t on the front. Once I can save up for a new hub I'll switch over to a Chris King. Good to know that I wont have to use a half link with the Rennen if I use a different gear ratio.

By the way... do you think the 22-19 will feel a lot different than 22-18?

[carnagr]

Enough different. I had 22-18 for a while, and it was way too hard. 22-19 I find still a bit hard, but it kicks the shit out of 22-18. I run 20-18, and would like something a little harder. 18-16, or 24-21 are really nice.

[Trialsaddict]

yeah i guess thats the advantage of having a sprung tensioner..... sprung is good.

I 2nd that. Tension the spring good, and ride on.

[felix]

Looking through some pictures I found one that is similar to your's, Lance.
I guess my legs are not as powerful as yours, but still my chain is far away from being well tensioned in that situation.
Under normal conditions the tension is okay though.