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Grip shift gear on kids bike difficult to turn

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lunerfish Offline
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Post: #1
Grip shift gear on kids bike difficult to turn
I've read other threads and lots of info online, and I'm still stuck. My son is unable to shift the gears on his new 6-gear bike. We tried adjusting the derailer to release some tension and tinkered with adjustments here and there, and nothing seems to be working. Is there anything that we can do? I really want him to be able to shift his own gears. Going uphill today we had to stop several times so that I could shift the gears for him.
Jan 7, 2010 09:48 PM
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Joe_W Offline
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Post: #2
RE: Grip shift gear on kids bike difficult to turn
Adjusting the cable tension will change the setup. If the bike is new, go back to the bike shop with it and talk to them, they might come up with a solution. What might help is looking at the cables and housing. Sometimes the housing is a bit too long, this will increase the friction but it is done to make it possible to change handlebar height etc. The housing can also be damaged (yes, also on a new bike) so look for kinks. What also might help is another derailleur, some of the cheaper ones are, well, cheap.
Jan 8, 2010 04:10 AM
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private Offline
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Post: #3
RE: Grip shift gear on kids bike difficult to turn
A similar problem. The bike is a Diamondback Cobra Jr. 20" mountain bike. It has a single right hand six speed twist/grip type shifter that is too hard to shift.

It requires substantial force to move from 6 to 1, especially from 3 to 1. Moving from 1 to 6 is not as difficult, but far too difficult for any child, and tiring (hurting) for an adult after a short while. This shifter is made by SunRace, the derailleur by Shimano.

The gears/derailleur are in good working order and adjusted correctly. The bike will shift correctly in both directions, but with way too much force needed, as mentioned.

On the SunRace website (apparently a company in Taiwan), they mention among the features of their twist/grip shifters a spec for a "force adjuster".

Does anyone have any information or experience with this?

While I agree with a vast majority of posts, largely apparently from dealers/repair shop professionals and seasoned enthusiasts, I am not interested in replacing or even repairing something brand new. This bike is not that "cheap" (at least to me) for a child's bike. Adjustments/break-in period is a given.

I would like to know if anyone has heard of a "force adjuster" on a shifter like this, and if they have any information on how to use it. Constructively and for the purpose intended, that is.
Mar 25, 2012 12:01 AM
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Morton Offline
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Post: #4
RE: Grip shift gear on kids bike difficult to turn
Same bike DB Cobra 20" and same problem except it flies from first gear to sixth gear. It is hard enough for me to turn towards first gear, let alone my five year old, but once I move it to first gear my son taps it to hard and it re-springs back to sixth gear. If there is anyway to fix it so that it has the ease of turning both ways it would be great information.

So from reading others post, I don't think this is a problem with every bike having a kinked line or having to replace any parts. I just bought this bike on Wednesday for an Easter gift (Yes we gave it to him early, nowhere to hide it) and as I read, there are a few others with the same problem.
Apr 7, 2012 04:15 PM
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private Offline
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Post: #5
RE: Grip shift gear on kids bike difficult to turn
An update on the Diamondback Cobra 20": After several more "sessions" of adjustment, the shifter still would not work correctly; still too stiff and/or unresponsive. I called the number for Diamondback (Raleigh Bikes) and was told they will send a new shifter (with cable) to me at no cost.

I will post here when I receive the new shifter and have at least tried to install and adjust it. For now I will reserve judgement on both Raleigh/Diamondback and SunRace.

To put this a little more in perspective, I recently (this January) replaced a similar SMRX six speed twist shifter on another 20" bike with no problem at all.
Apr 7, 2012 11:52 PM
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ghost Offline
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Kent, UK
Posts: 107
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Post: #6
RE: Grip shift gear on kids bike difficult to turn
(Apr 7, 2012 11:52 PM)private Wrote:  An update on the Diamondback Cobra 20": After several more "sessions" of adjustment, the shifter still would not work correctly; still too stiff and/or unresponsive. I called the number for Diamondback (Raleigh Bikes) and was told they will send a new shifter (with cable) to me at no cost.

I will post here when I receive the new shifter and have at least tried to install and adjust it. For now I will reserve judgment on both Raleigh/Diamondback and SunRace.

To put this a little more in perspective, I recently (this January) replaced a similar SMRX six speed twist shifter on another 20" bike with no problem at all.

If it is a new bike then take it back and have the unit replaced. Apart from lubing it,there is not much that can be done. If it is tight then it will only get worse. They are nearly all plastic with a steel clip on the inside. Our rebuild concern always change them to a suitable indexing thumb unit. It is unfortunate that your bike started out in this condition. Let us all know how it turns out.

Cycle the streets of Bristol!
Apr 8, 2012 04:02 AM
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Morton Offline
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Post: #7
RE: Grip shift gear on kids bike difficult to turn
Thanks for the info, but the one problem is, I have no clue how to put something like that on the bike. I could try but I might just make it worse.

Also taking it to the place we bought it is not an option either. We bought it on the military base at the Navy Exchange, so it wasn't a regular bike store, nor do they have anyone skilled enough to change it. We do have a Trek store down the road from us, I'm wondering if Diamond Back would be willing to pay the Labor cost as well.
Apr 8, 2012 06:36 AM
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ghost Offline
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Kent, UK
Posts: 107
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Post: #8
RE: Grip shift gear on kids bike difficult to turn
(Apr 8, 2012 06:36 AM)Morton Wrote:  Thanks for the info, but the one problem is, I have no clue how to put something like that on the bike. I could try but I might just make it worse.

Also taking it to the place we bought it is not an option either. We bought it on the military base at the Navy Exchange, so it wasn't a regular bike store, nor do they have anyone skilled enough to change it. We do have a Trek store down the road from us, I'm wondering if Diamond Back would be willing to pay the Labor cost as well.

I am sure Trek would do it. Not sure who would pay for it though. Buying bikes from an unknown bike place is ALWAYS a crapshoot.

Cycle the streets of Bristol!
Apr 8, 2012 10:53 AM
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Pete Offline
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Post: #9
RE: Grip shift gear on kids bike difficult to turn
Same bike, DB20, same issue. After a lot of tinkering, I've come to believe the weight (strength/duty) of the spring inside the Shimano derailleur is not well-matched to the Sunrace twist shifter. This derailleur is designed to work best with shifting mechanism with greater leverage by design. The greater leverage would have the effect of pulling against the force of the spring easier when shifting down (and effectively up in gear size) given the travel the derailleur must make. The best solution is a lighter duty spring--and thus different derailleur since the spring is captured in a permanent housing. In short, bad engineering on Diamondback's part for having mismatched the shifter/derailleur combo.

I'm planning to put a call into DB and request they send me a replacement part of a different spec on one end or the other.
Jul 6, 2012 03:57 PM
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private Offline
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Post: #10
RE: Grip shift gear on kids bike difficult to turn
(Apr 8, 2012 04:02 AM)ghost Wrote:  
(Apr 7, 2012 11:52 PM)private Wrote:  An update on the Diamondback Cobra 20": After several more "sessions" of adjustment, the shifter still would not work correctly; still too stiff and/or unresponsive. I called the number for Diamondback (Raleigh Bikes) and was told they will send a new shifter (with cable) to me at no cost.

I will post here when I receive the new shifter and have at least tried to install and adjust it. For now I will reserve judgment on both Raleigh/Diamondback and SunRace.

To put this a little more in perspective, I recently (this January) replaced a similar SMRX six speed twist shifter on another 20" bike with no problem at all.

If it is a new bike then take it back and have the unit replaced. Apart from lubing it,there is not much that can be done. If it is tight then it will only get worse. They are nearly all plastic with a steel clip on the inside. Our rebuild concern always change them to a suitable indexing thumb unit. It is unfortunate that your bike started out in this condition. Let us all know how it turns out.

Update: I did contact the manufacturer and they did send a new shifter, free of charge. I installed and adjusted it as per manufacturer's specs. I trimed and lubed the inside of the cable housings as well. The results were mediocure. I agree with Pete's assesment of the derailleur/shifter being mismatched. I also agree with the post that a lever shifter might be better, provided it too is in sync with the rest of the system.

It almost seems this type of shifter puts too much strain on smaller wrists, even when it works correctly. A thumb shifter might not be good for the weakest joint on the human body either (especially one that is still growing).

One other thing to consider regarding shifting at all, this bike is HEAVY for it's size. The body is apparently steel (magnets attach everywhere). Even when I put it in the "easy" gear, a fairly strong child found it a bit taxing on up hill dirt/gravel trails.

This problem is on-going, so I will continue to review and post and hopefully we can all find an acceptable solution. I suspect I will eventually have to find a different type of lever shifter.
Jul 7, 2012 02:59 AM
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lacotter Offline
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Post: #11
RE: Grip shift gear on kids bike difficult to turn
I just bought my son this bike for his birthday - and he is already crying because the gears don't work Sad what a bummer. I am having the same problem as everyone else (and lots of these complaints on Amazon reviews too), I would be interested to know if anyone has found something that works. One person on Amazon said they just changed out the grip twister to a SRAM, has anyone else done this? I would be willing to try it, just not sure what to buy.

Thanks
Sep 2, 2012 06:05 AM
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lacotter Offline
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Post: #12
RE: Grip shift gear on kids bike difficult to turn
Here is a note about the shifter from another site:
http://stevethebikeguy.com/?p=950

I really wish Diamondback would not sell this bike with a known issue.
Sep 2, 2012 06:16 AM
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Bill Offline
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NY,USA
Posts: 2,765
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Post: #13
RE: Grip shift gear on kids bike difficult to turn
As for the information thanks for sharing. Being the bike is heavy as a barge another way to make it easier is to change the gear ratio on the freewheel? Now for the shifter, going to friction thumb shifters probably would be 10x easier then this fistgrip ooops I mean twist grip lol.

Good maintenance to your Bike, can make it like the wheels are, true and smooth!
Sep 3, 2012 05:43 AM
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nfmisso Offline
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San Jose, CA
Posts: 2,273
Joined: Jul 2010
Post: #14
RE: Grip shift gear on kids bike difficult to turn
I do not have the particular bike, but I do have four bikes (three 7 sp, one 8 sp) with SRAM MRX shifters in conjunction with three different Shimano derailleurs. It does not take a great deal of effort to shift up or down; the force required should be no trouble for an 8 year old.

The SRAM MRX works better than Shimano's grip shift. I have no experience with the Sunrace grip shift.

Regarding the bike's weight - changing the rims to aluminum is the mos effective reduction to cycling effort because mass of the rims hits in two ways. (1) bike weight. (2) rotating inertia - the wheels are flywheels that need to be spun up and slowed down. Reducing rotating inertia means the bike will accelerate faster with the same effort, stop faster, and overall be much less tiring to ride.

Nigel
Sep 3, 2012 10:48 AM
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jas001 Offline
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Post: #15
RE: Grip shift gear on kids bike difficult to turn
Just an FYI on the Diamondback bike - I had the same problem, called Diamondback and they are shipping me a new SRAM shifter for free. They are very well aware of this problem and have solved it on the newer or nextgen bikes.
Nov 15, 2012 02:58 PM
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adarsh Offline
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Post: #16
RE: Grip shift gear on kids bike difficult to turn
(Jan 7, 2010 09:48 PM)lunerfish Wrote:  I've read other threads and lots of info online, and I'm still stuck. My son is unable to shift the gears on his new 6-gear bike. We tried adjusting the derailer to release some tension and tinkered with adjustments here and there, and nothing seems to be working. Is there anything that we can do? I really want him to be able to shift his own gears. Going uphill today we had to stop several times so that I could shift the gears for him.

the grip shifters are not good you can replace with thumb shifters which are 1000 times better than grip shifters Wink
Feb 23, 2013 09:18 PM
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