Myron400

I purchased a used Next Nitro 21speed bike. I need to change the gear cables (handle bar grip style), and possibly the front and rear derailer. Sunrun is the current brand installed. Is it possible to change out to a different brand, as I am having trouble finding the Sunrun brand in stock.

Charliekeet

Yes, you should do so. Try to get Shimano or Jagwire cables and/or housing, as either of those brands will be an improvement and much easier to find. For derailleurs, again, Shimano.

Iride01 

How old is this bike? Shifter cables changed diameters back before the century changed. If it were down tube shifters I say no big deal. But sounds like you are saying this is a twist grip shifter.

Some of the cable ends are a little different too. If you are going to a bike shop to get cable, then take the bike with you. Otherwise, pull the cable out and look at the end and compare before you buy.

Myron400

Thanks for your replies. I am new at trying to repairing a bike. I am not sure of the age of the bike. The rear wheel has 7 cassettes (21 speed). As I understand your response, I could purchase a Shimano gear cable, and a derailer set up for 7 cassettes. Is this correct?

Iride01 

I wouldn't begin to guess until I knew what model and part number the shifter is. Not all of us know what a Next Nitro is off the top of our heads, nor do we know that the previous owner didn't change out the components to something else.

If you have a pic, you can upload it somewhere and then write the share link in the plain text of your message. Delete the https:// and put a space on both sides of any . in the url.


Which is yours... though 3 of these are brake, two are shifter. I'm not sure the Shimano will fit a Campy shifter.

https://www.bikeman.com/bicycle-repa...bles-a-housing

Andrew R Stewart 

Not all twist grip shifters allow cable replacement. There are some that are OEM on real cheap "big box" store bikes that have the assembly of the twist grips such that accessing the cable is all but impossible w/o damaging the shifter. I don't remember the labeled brands but we do come across them from time to time. In a few cases the customer didn't want to pay for a SRAM MRX shifter, other times we have replaced the shifter with usually good results. Pretty much all the "off brands" of gear systems we see are Shimano indexing spec compatible. Although the cheap materials, design and construction found with the rest of these gear systems often limit the "performance" of a brand name shifter.

As long as the rest of the bike merit the cost I do suggest replacing the shifters if the cable replacement proves to be impossible. Andy

oldukbkr 

As Andy noted above the shifter needs to be compatible with the derailleur. Some brands - e.g. SRAM & Shimano - don't play well together. Using a Shimano derailleur gives you a good chance of it being compatible with your shifter. If the bike is worth it, I agree with Andy's suggestion to replace shifter and derailleur - use the same brand to ensure compatibility.

JoeTBM 

Andy, I'm very curious on your response here on twist shifters and cable replacement ability. As we get donated many big-box store bikes, we have seen our share of non-functioning grip shifters.

The only times we don't attempt a cable replacement is if the twist shifter is cracked or otherwise worn/damaged. I'm curious which twist shifters you are referring to that have problem accessing the cable for replacement. Yes I agree, some need some special attention/finesse to disassemble and reassemble and sometimes three hands, but so far I think we have been pretty successful in resurrecting those dead twist shifters with a new cable. We even have a box with salvaged grips, leaf springs and other goodies salvaged from cracked/non-repairable shifters to help restore others.

Andrew R Stewart 

Joe- Sorry but I don't remember the name of the shifters. They were cheap feeling with rather bulky bodies and hard grips. I'll try to make a note next time we see a pair.

Now the vast majority of twist grip shifters we see are SRAM or Shimano and these have cable replacement provisions. I just a few days ago replaced a cable on one of the earlier generations of Grip Shift. It still had the plastic spring. Andy

Andrew R Stewart 

So I learned something the other day. I had a repair job on a cheap bike that included replacing the twist grip shifters. The OEMs were of the type I posted about above. After doing the new shifter installs I took a better look at the old ones and now see that they can be taken apart to replace the cable. But to do so the shifter has to be removed from the bars so the 4 tabs on the stationary part can be flexed inward to release the rotating portion. Once this is done the cable can be accessed. (See the photo) This turns a 5 minute job into a 15 minute one and risks the grips too. Great design Andy

JoeTBM 

Totally agree this type is more of a pain and requires them to be removed from the handlebars including removal of the grip which could be destroyed in the process. Thanks for the follow-up.