Grip shift gear on kids bike difficult to turn

[lunerfish]

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.

[Joe_W]

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.

[private]

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.

[Morton]

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.

[private]

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.

[ghost]

(04-08-2012, 02:52 AM)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.

[Morton]

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.

[ghost]

(04-08-2012, 09:36 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.

[Pete]

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.

[private]

(04-08-2012, 07:02 AM)ghost Wrote:  

(04-08-2012, 02:52 AM)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.

[lacotter]

I just bought my son this bike for his birthday - and he is already crying because the gears don't work 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

[lacotter]

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.

[Bill]

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.

[nfmisso]

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.

[jas001]

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.

[adarsh]

(01-08-2010, 12:48 AM)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

[Will L.]

(01-08-2010, 12:48 AM)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.

SOLUTION. I HAD the same problem on my 2001 Walmart mtb. Wasted almost 2 days on it. I Finally looked at a discarded bike I found with similar Shimano equipment that worked. It was just a cable routing issue. On the derailleur arm where my cable pinch bolt is there is a little "ear". I had the cable running between the "ear" and the pinch bolt. The cable is supposed to run OUTSIDE of the "ear". The cable won't rest on the "ear" itself but will be beside it. This tiny change makes the cable pull a little bit towards the left side of the bike instead of just about straight down. This gives the cable more leverage so you don't have to turn the grip shifter as hard for it to move the derailleur. Anyway don't turn the grip shifter very hard or you might break a little plastic part inside. The derailleur had been working fine before I had to replace my broken shifter so this was frustrating. The pic shows the top view on the discarded bike. The "ear" is on the right side of the pinch bolt where the cable turns downward. If the cable is between the pinch bolt and the ear your shifter won't work.

[CMT]

I’m new here, thanks for reading my issue. I am having difficulty with my daughters 7 speed bike. We bought it for her for Easter, and the shifter worked fine up until about a month ago. The shifter became very hard to turn, even for me. Then it was impossible to turn. I tried several nights making adjustments, but I couldn’t fix it. So we finally just bought a new shifter. Now I can’t get it adjusted properly, it won’t shift to 1st or 7th gears, even when that is what the shifter reads. I’ve screwed/unscrewed all the adjusters multiple times in different combinations, but no luck. Loosened/tightened the cable, nothing works. There is an unknown I’m dealing with. I’m not a bike mechanic by any means, but a simple installation like this I get should take a max of 10-15 minutes. The derailer doesn’t look like it is bent, either. Thanks in advance for any assistance!

[Jesper]

(08-08-2020, 09:58 PM)CMT Wrote:  I’m new here, thanks for reading my issue. I am having difficulty with my daughters 7 speed bike. We bought it for her for Easter, and the shifter worked fine up until about a month ago. The shifter became very hard to turn, even for me. Then it was impossible to turn. I tried several nights making adjustments, but I couldn’t fix it. So we finally just bought a new shifter. Now I can’t get it adjusted properly, it won’t shift to 1st or 7th gears, even when that is what the shifter reads. I’ve screwed/unscrewed all the adjusters multiple times in different combinations, but no luck. Loosened/tightened the cable, nothing works. There is an unknown I’m dealing with. I’m not a bike mechanic by any means, but a simple installation like this I get should take a max of 10-15 minutes. The derailer doesn’t look like it is bent, either. Thanks in advance for any assistance!

Hi CMT,
Welcome to the site. First, since the bike is not that old, it should be covered by a warranty for defective parts and workmanship; if you got this from a "big box" retailer and assembled it yourself, I don't know how that might affect the warranty coverage; but if it was assembled at the store for you then I would expect it to be fully covered. The same applies to having a bike shipped to you and doing the assembly yourself. If it worked properly for a month, then it should work properly for a few months barring any incidental damage which occurred in the interim.

I am not a fan of grip shifters if this is what you have. Due to that fact, I have none on any bike, my best advice since I really don't work on this style (I generally trade them out with a "thumb" shifters) is to mark your cable where it is clamped onto the derailleur and then disconnect the cable. If, when cycling the shifter through its range of movement, the grip moves freely then the problem is most likely related to the derailleur. Grab the derailleur by hand and try to move it; it will have some tension provided by the spring, but should still move freely. If the grip does not move freely than it is most likely the shifter and/or the cable/housing causing the problem. Usually a simple examination of the cable housing will suffice. If you see no extreme bends or kinks in the housing, the cable should be able to move through it without binding. Take note that the cable when reconnected to the derailleur and under load has greater friction involved and will make it move a little harder than when unconnected, but this should still not cause the grip shifter the be difficult to move. If you feel the need to replace the part, I would consult a bike shop on a recommended replacement part that will not have the same problem. There may be an adjustment on the grip assembly for the amount of effort required to shift, but I am not familiar enough with these to tell you where it might be (if indeed there is one), or what would be the best means of adjusting it.

If you do not feel confident doing this work then bring it to a shop and have them check it out. This seems to be a common problem with children's bikes and less costly adult bike since quite often the parts used are not of the highest quality both in function and durability.

I, personally, would have this taken care of as a warranty repair if at all possible. You should not have to pay for this problem to be resolved with a bike that new.

[Jesper]

Quick note: although I don't think that this relates to your original issue, it may relate to your problem after you installed the new part. When you mentioned adjusting the derailleur and not being able to get it to shift into 1 or 7; you may have inadvertently adjusted the "high" and "low" limit screws where they are preventing the derailleur from travelling through its full range. This of course does not explain why the shifter stopped working properly after a month or so before you attempted to remedy the problem; even then, these adjustments may not have been correctly set when the bike was first assembled. These adjustments can certainly cause you from being able to shift to all gears and/or cause the chain to be "dropped" and moved completely off the gear. Photos might help since kids bikes aren't always the same as an adult bike concerning the type of components installed. Anything helps; I'm kind of "shooting in the dark" trying to determine why there was a problem at the start with original equipment, and now with the replacement part.