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Krix 05-08-21 07:14 PM

Tiagra question
 
Hi guys,

I have a Tiagra ST4700 10 speed STI and a 11-42 Deore Cassette 10 speed.

is there any way for me for this to work? What rear derailleur and hubs should I buy? Will i need to buy a road link?

Thank you

DorkDisk 05-08-21 07:16 PM


Originally Posted by Krix (Post 22051003)
Hi guys,

I have a Tiagra ST4700 10 speed STI and a 11-42 Deore Cassette 10 speed.

is there any way for me for this to work? What rear derailleur and hubs should I buy? Will i need to buy a road link?

Thank you

A road derailleur will not wrap 42t, I believe the max is 34.

Krix 05-08-21 07:18 PM


Originally Posted by DorkDisk (Post 22051005)
A road derailleur will not wrap 42t, I believe the max is 34.

how bout an mtb derailleur? Maybe like deore m4120 sgs

DorkDisk 05-08-21 07:22 PM


Originally Posted by Krix (Post 22051009)
how bout an mtb derailleur? Maybe like deore m4120 sgs

The M4120 long cage will wrap 42t. The shifters have to be compatible with the derailleur though.

Krix 05-08-21 07:28 PM


Originally Posted by DorkDisk (Post 22051013)
The M4120 long cage will wrap 42t. The shifters have to be compatible with the derailleur though.

i have a STI Tiagra ST4700. Will it be okay?

DorkDisk 05-08-21 07:31 PM


Originally Posted by Krix (Post 22051021)
i have a STI Tiagra ST4700. Will it be okay?

I don't think so, the cable pull is different. GRX RX812 will work

Krix 05-08-21 07:44 PM


Originally Posted by DorkDisk (Post 22051027)
I don't think so, the cable pull is different. GRX RX812 will work

Please correct me if im wrong but GRX needs to be in DI2? I am not sure what it is though but it's different from the cables right? Will it be okay?

dedhed 05-08-21 08:05 PM

Tiagra 4700 is an odd duck. 10 speed but uses 11 speed road cable pull on 10 speed cassette.

​​​​​​Science Behind the Magic | Drivetrain Compatibility ? Art's SLO Cyclery

Russ Roth 05-08-21 08:24 PM


Originally Posted by Krix (Post 22051045)
Please correct me if im wrong but GRX needs to be in DI2? I am not sure what it is though but it's different from the cables right? Will it be okay?

No, if it is a cable pull GRX der then it will work with 4700 Tiagra. I'm not familiar enough with GRX to know if there is a DI2 line, maybe in the 800 level, but the 400 series is 10sp cable, and the 600 series is 11sp cable.

DorkDisk 05-08-21 08:44 PM

GRX is available in Di2 or cable. The cable pull is 11sp road, the same as Tiagra 4700 10sp.

oldbobcat 05-08-21 10:05 PM


Originally Posted by DorkDisk (Post 22051013)
The M4120 long cage will wrap 42t. The shifters have to be compatible with the derailleur though.

Aye, that's the rub. According to Art's Cyclery (Science Behind the Magic | Drivetrain Compatibility ? Art's SLO Cyclery), Shimano an 11-speed road rear shifter pulls 3.1mm per click. Shimano 10-speed pulls 2.3 mm. Shimano 10-speed mountain derailleurs want 3.4 mm. Tiagra 4700 works like Shimano 11 but for 10, so, for lack of better info, I'd assume it pulls 3.1.

By the way, riders have been mixing Shimano 10-speed road (2.3 mm) with 9-speed MTB (2.5 mm) with considerable success. Buena sera.

70sSanO 05-08-21 10:37 PM

When I go the Art’s it shows...
Shimano 10 speed Road cable pull = 2.3mm
Shimano 11 speed Road cable pull = 2.7mm

10 speed cassettes are spaced at 3.95mm ctc.
11 speed cassettes are spaced at 3.74mm ctc.

I think it is just math.
10 speed road RD actuation - 3.95/2.3 = 1.7
11 speed road RD actuation - 3.74/2.7 = 1.4

Tiagra 4700 shifter cannot pull the same as 11 speed cable pull because you can use an 11 speed RD and move it 3.95mm.

Tiagra 4700 pull - 3.95/1.4 (RD actuation) = 2.8mm cable pull.

If it is correct that any Shimano 11 speed road RD works with Tiagra 4700 shifters, then 11 speed GRX RD should work with Tiagra 4700 shifters and a 10 speed cassette.

John


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