Is this compatible for 8 speed?

Not perfectly - the m3100 model is really meant for 9 speed

Will this replace the stx rc on a Trek 7300 8 speed?

Shimano's Compatibility charts won't show this "9-speed" derailleur as compatible with 8-speed components, but it should work just fine. Shimano 8-speed shifters will work. This RD can handle larger cogs than were common in the 8-speed era, up to 36t largest cog, but assuming you have 11-32 it'll work. I have an stx rc RD on one of my bikes, and wouldn't hesitate to try this as a replacement.

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Black,ERDM3100SGS Alivio Alivio M3100 Rear derailleur, 9-Speed, Shadow Design, SGS Long cage

Product ID: 241101188

Details

Brand
SHIMANO
Color
Black
Item Weight
0.2 kg
Material
other
Mounting Type
Braze-On Mount

⚙️9-speed precision shifting

⛰️SGS long cage for rugged trail use

🛡️Shadow RD tech for derailleur protection

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Description

⚙️ Shift like a pro, conquer every trail with confidence!

HYPER GLIDE SYSTEM - Protects drivetrain components from premature wear, extending your bike’s performance lifespan.
SHADOW RD TECHNOLOGY - Sleek, low-profile design minimizes damage risk from trail obstacles—ride harder, worry less.
DURABLE LONG CAGE DESIGN - SGS long cage optimizes chain tension and stability for aggressive trail and trekking adventures.
SEAMLESS 9 SPEED SHIFTING - Experience ultra-smooth gear transitions that keep your cadence flawless on every climb and descent.
LIGHTWEIGHT ROBUST BUILD - Crafted from steel and aluminum for a perfect balance of strength and minimal weight at just 0.2 kg.

The Shimano Alivio M3100 Rear Derailleur is a high-performance 9-speed drivetrain component featuring Shadow RD technology for enhanced protection and a sleek profile. Its SGS long cage design ensures optimal chain tension and durability on rugged trails, while the HyperGlide system extends drivetrain life. Lightweight yet robust, this derailleur is engineered for serious trail and trekking cyclists seeking reliable, smooth shifting under all conditions.

Specifications

ASIN	B08CGYD213
Best Sellers Rank	#53,139 in Sports & Outdoors ( See Top 100 in Sports & Outdoors ) #17 in Rear Bike Derailleurs
Brand	SHIMANO
Brand Name	SHIMANO
Case Material Type	Steel & Aluminum
Color	Black
Customer Reviews	4.6 out of 5 stars 696 Reviews
Global Trade Identification Number	04550170621155
Included Components	Bike Parts
Item Dimensions L x W x H	6.69"L x 4.43"W x 3.94"H
Item Type Name	Rear derailleur.
Item Weight	0.2 kg
Manufacturer	Shimano
Manufacturer Part Number	ERDM3100SGS
Material	other
Material Type	other
Model Number	C8C086
Mount Type	Braze-On Mount
Mounting Type	Braze-On Mount
Number of Items	1
Number of Teeth	36
Product Dimensions	6.69"L x 4.43"W x 3.94"H
UPC	192790621159
Unit Count	1 Count
Warranty Description	2 Year Manufacturer

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65456CFA

Duties & taxes included

In stock

Sold byAmazon SenegalDelivered byDesertcartCustomer service byDesertcartReturns14 days · 30 with PRO

Buyer Protection · Full refund if your order doesn't arrive as described.

Desertcart purchases this item on your behalf and handles shipping, customs, and support to Senegal.

Secure transaction

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