bigalgeorge

There is possibly no way to do this, but I have a Shimano TY300 (Tourney) derailleur and its almost new.
Ive purchased several Ebikes of same type and all transitions from High to Low are all the same; hard to actuate but the other way Low to High is easy. Clearly, the cables which are new are consistent, there appears nothing defective in the setups, I feel its the spring tension within the derailleur which in this low-end model possible cant be adjusted, but can it be replaced or altered?
Thanks, Al.

Andrew R Stewart 

Not exactly sure what is being asked but I'll give this a shot. Yes, the der movement from high to low is working against the parallelogram return spring. From low to high the spring aids movement. So there's more lever effort to go to lower gears (on the rear) then when going to higher gears. This is normal for all "hi/normal" ders (pretty much all current ones). Shimano has produced "low/normal" (jokenly called "rapid demise" by some mechanics) that have the parallelogram spring reversed in action. The der sits under the low gear cog when the cable is at it's most relaxed state.

The parallelogram return spring is not usually adjustable. On such an entry level component the cost savings often comes from minimal features, sloppy construction and greater performance drop off with wear/time. Andy

bigalgeorge

Thanks Andy. Most helpful. Any recommendations as to a replacement drail that is economic as in below $20?

Andrew R Stewart 

I've felt that the Altus/Acera der design is far better at shifting then the Tourney's. As to price, that's your bag. Andy

bigalgeorge

Hi Ive got a Shimano TX35 arriving soon, their part numbers are a bit confusing the TX35 might perform the same as TY300 as its called a Tourney as well.

Out of the shimano ACERA RD-M390 and SHIMANO Altus RD-M370 which one would you go for a 7 speed shift?

Bill Kapaun

Tourney works fine for 7 speed or less. Altus isn't much more $ and a step up.
You didn't specify how many "speeds" you had, but if a 7 or less, you don't want to go "too high end". They are made for narrower chains & cogs and will give you chain rub sooner with minor cross chaining.

As far as shift effort-
When shifting to a larger cog/ring, think of jacking something up with a hydraulic jack.
When shifting the opposite, think of it as a quick, predetermined opening/closing of the valve. You don't have to jack it "down".
Which takes more effort?
I guess winding a clock is somewhat similar?

bigalgeorge

As mentioned earlier 7-speed. By the sound of it Im not going to achieve much by upgrading from a Tourney.
Its a pity user cant adjust spring tension as well, which Im thinking would be the main force issue.
Looking at Altus images, it does look higher quality, but the leverage on the rail seems similar.

dsbrantjr

You could also look at the Microshift derailleurs, they are Shimano-compatible. I have found them to perform well and be a good value. I know of no derailleurs which allow indexing spring force adjustment.

bigalgeorge

Hi Im just wondering the 7-speed Shimano TX35 thats coming is short cage vs TY300 long cage. Physics suggest that the short cage = less pull effort??

Ive found Microshift RD-M25S RD-M29 RD-M45 no idea which might best suit 11t-28t chainwheel.